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1. general description the sc16c754b is a quad universal asynchronous receiver/transmitter (uart) with 64-byte fifos, automatic hardware/software ?ow control, and data rates up to 5 mbit/s (3.3 v and 5 v). the sc16c754b offers enhanced features. it has a transmission control register (tcr) that stores receiver fifo threshold levels to start/stop transmission during hardware and software ?ow control. with the fifo ready (fifo rdy) register, the software gets the status of txrd y/ rxrd y for all four ports in one access. on-chip status registers provide the user with error indications, operational status, and modem interface control. system interrupts may be tailored to meet user requirements. an internal loopback capability allows on-board diagnostics. the uart transmits data, sent to it over the peripheral 8-bit bus, on the tx signal and receives characters on the rx signal. characters can be programmed to be 5, 6, 7, or 8 bits. the uart has a 64-byte receive fifo and transmit fifo and can be programmed to interrupt at different trigger levels. the uart generates its own desired baud rate based upon a programmable divisor and its input clock. it can transmit even, odd, or no parity and 1, 1.5, or 2 stop bits. the receiver can detect break, idle, or framing errors, fifo over?ow, and parity errors. the transmitter can detect fifo under?ow. the uart also contains a software interface for modem control operations, and has software ?ow control and hardware ?ow control capabilities. the sc16c754b is available in plastic lqfp64, lqfp80 and plcc68 packages. 2. features n 4 channel uart n 5 v, 3.3 v and 2.5 v operation n pin compatible with sc16c654ia68, tl16c754, and sc16c554ia68 with additional enhancements, and software compatible with tl16c754 n up to 5 mbit/s data rate (at 3.3 v and 5 v; at 2.5 v maximum data rate is 3 mbit/s) n 5 v tolerant on input only pins 1 n 64-byte transmit fifo n 64-byte receive fifo with error ?ags n industrial temperature range ( - 40 c to +85 c) n programmable and selectable transmit and receive fifo trigger levels for dma and interrupt generation sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos rev. 04 6 october 2008 product data sheet 1. for data bus pins d7 to d0, see t ab le 24 limiting v alues .
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 2 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos n software (xon/xoff)/hardware ( r ts/ cts) ?ow control u programmable xon/xoff characters u programmable auto- r ts and auto- cts n optional data ?ow resume by xon any character n dma signalling capability for both received and transmitted data n supports 5 v, 3.3 v and 2.5 v operation n software selectable baud rate generator n prescaler provides additional divide-by-4 function n fast data bus access time n programmable sleep mode n programmable serial interface characteristics u 5, 6, 7, or 8-bit characters u even, odd, or no-parity bit generation and detection u 1, 1.5, or 2 stop bit generation n false start bit detection n complete status reporting capabilities in both normal and sleep mode n line break generation and detection n internal test and loopback capabilities n fully prioritized interrupt system controls n modem control functions ( cts, r ts, dsr, dtr, ri, and cd) n sleep mode 3. ordering information table 1. ordering information type number package name description version sc16c754bibm lqfp64 plastic low pro?le quad ?at package; 64 leads; body 7 7 1.4 mm sot414-1 sc16c754bib80 lqfp80 plastic low pro?le quad ?at package; 80 leads; body 12 12 1.4 mm sot315-1 sc16c754bia68 plcc68 plastic leaded chip carrier; 68 leads sot188-2
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 3 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 4. block diagram fig 1. block diagram of sc16c754b dtra to dtrd rtsa to rtsd transmit fifo registers txa to txd receive shift register receive fifo registers rxa to rxd interconnect bus lines and control signals sc16c754b transmit shift register xtal2 xtal1 002aaa866 intsel flow control logic clksel data b u s and control logic register select logic interrupt control logic d0 to d7 ior iow reset a0 to a2 csa to csd inta to intd txrdy rxrdy clock and baud rate generator modem control logic ctsa to ctsd ria to rid cda to cdd dsra to dsrd flow control logic
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 4 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 5. pinning information 5.1 pinning fig 2. pin con?guration for lqfp64 sc16c754bibm dsra dsrd dtra dtrd v cc rtsa rtsd inta intd txa txd iow ior txb txc csb intb intc rtsb rtsc gnd v cc dtrb dtrc ctsb dsrb cda cdb ria rib rxa gnd v cc d7 a2 d6 a1 d5 a0 d4 xtal1 d3 xtal2 d2 reset d1 gnd d0 rxc v cc ric rxd cdc dsrc cdd 002aab564 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 gnd rxb rid ctsa csa ctsc csc csd ctsd
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 5 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 3. pin con?guration for lqfp80 sc16c754bib80 n.c. n.c. n.c. dsrd dsra ctsd ctsa dtrd dtra gnd v cc rtsd rtsa intd inta csd csa txd txa ior iow txc txb csc csb intc intb rtsc rtsb v cc gnd dtrc dtrb ctsc ctsb dsrc dsrb n.c. n.c. n.c. n.c. n.c. n.c. cda cdb ria rib rxa rxb gnd clksel d7 n.c. d6 a2 d5 a1 d4 a0 d3 xtal1 d2 xtal2 d1 reset d0 rxrdy intsel txrdy v cc gnd rxd rxc rid ric cdd cdc n.c. n.c. n.c. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 002aaa867
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 6 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 5.2 pin description fig 4. pin con?guration for plcc68 sc16c754bia68 dsra dsrd ctsa ctsd dtra dtrd v cc gnd rtsa rtsd inta intd csa csd txa txd iow ior txb txc csb intb rtsb gnd dtrb ctsb dsrb csc intc rtsc v cc dtrc ctsc dsrc cdb gnd rib d7 rxb d6 clksel d5 cda ria rxa n.c. d4 a2 d3 a1 d2 a0 d1 xtal1 d0 xtal2 intsel reset rxrdy txrdy gnd rxc ric cdc v cc rxd rid cdd 002aaa868 10 11 12 13 14 15 16 17 18 19 20 60 59 58 57 56 55 54 53 52 51 50 21 22 23 24 25 26 49 48 47 46 45 44 27 28 29 30 31 32 33 34 35 36 37 6 5 4 3 2 1 68 67 66 65 64 9 8 7 38 39 40 41 42 43 63 62 61 table 2. pin description symbol pin type description lqfp64 lqfp80 plcc68 a0 24 30 34 i address 0 select bit. internal registers address selection. a1 23 29 33 i address 1 select bit. internal registers address selection. a2 22 28 32 i address 2 select bit. internal registers address selection. cd a64 79 9 i carrier detect (active low). these inputs are associated with individual uart channels a through d. a logic low on these pins indicates that a carrier has been detected by the modem for that channel. the state of these inputs is re?ected in the modem status register (msr). cdb 18 23 27 cdc 31 39 43 cdd 49 63 61 clksel - 26 30 i clock select. clksel selects the divide-by-1 or divide-by-4 prescalable clock. during the reset, a logic 1 (v cc ) on clksel selects the divide-by-1 prescaler. a logic 0 (gnd) on clksel selects the divide-by-4 prescaler. the value of clksel is latched into mcr[7] at the trailing edge of reset. a logic 1 (v cc ) on clksel will latch a logic 0 into mcr[7]. a logic 0 (gnd) on clksel will latch a logic 1 into mcr[7]. mcr[7] can be changed after reset to alter the prescaler value. this pin is associated with lqfp80 and plcc68 packages only. this pin is connected to v cc internally on lqfp64 package.
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 7 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos csa 7 9 16 i chip select (active low). these pins enable data transfers between the user cpu and the sc16c754b for the channel(s) addressed. individual uart sections (a, b, c, d) are addressed by providing a logic low on the respective csa through csd pins. csb 11 13 20 csc 38 49 50 csd 42 53 54 ctsa 2 4 11 i clear to send (active low). these inputs are associated with individual uart channels a through d. a logic 0 (low) on the cts pins indicates the modem or data set is ready to accept transmit data from the sc16c754b. status can be tested by reading msr[4]. these pins only affect the transmit and receive operations when auto- cts function is enabled via the enhanced feature register efr[7] for hardware ?ow control operation. ctsb 16 18 25 ctsc 33 44 45 ctsd 47 58 59 d0 to d7 53, 54, 55, 56, 57, 58, 59, 60 68, 69, 70, 71, 72, 73, 74, 75 66, 67, 68, 1, 2, 3, 4, 5 i/o data bus (bidirectional). these pins are the 8-bit, 3-state data bus for transferring information to or from the controlling cpu. d0 is the least signi?cant bit and the ?rst data bit in a transmit or receive serial data stream. dsra 1 3 10 i data set ready (active low). these inputs are associated with individual uart channels a through d. a logic 0 (low) on these pins indicates the modem or data set is powered-on and is ready for data exchange with the uart. the state of these inputs is re?ected in the modem status register (msr). dsrb 17 19 26 dsrc 32 43 44 dsrd 48 59 60 dtra 3 5 12 o data terminal ready (active low). these outputs are associated with individual uart channels a through d. a logic 0 (low) on these pins indicates that the sc16c754b is powered-on and ready. these pins can be controlled via the modem control register (mcr). writing a logic 1 to mcr[0] will set the dtr output to logic 0 (low), enabling the modem. the output of these pins will be a logic 1 after writing a logic 0 to mcr[0], or after a reset. dtrb 15 17 24 dtrc 34 45 46 dtrd 46 57 58 gnd 14, 28, 45, 61 16, 36, 56, 76 6, 23, 40, 57 i signal and power ground. inta 6 8 15 o interrupt a, b, c, and d (active high). these pins provide individual channel interrupts inta through intd. inta through intd are enabled when mcr[3] is set to a logic 1, interrupt sources are enabled in the interrupt enable register (ier). interrupt conditions include: receiver errors, available receiver buffer data, available transmit buffer space, or when a modem status ?ag is detected. inta to intd are in the high-impedance state after reset. intb 12 14 21 intc 37 48 49 intd 43 54 55 intsel - 67 65 i interrupt select (active high with internal pull-down). intsel can be used in conjunction with mcr[3] to enable or disable the 3-state interrupts inta to intd or override mcr[3] and force continuous interrupts. interrupt outputs are enabled continuously by making this pin a logic 1. driving this pin low allows mcr[3] to control the 3-state interrupt output. in this mode, mcr[3] is set to a logic 1 to enable the 3-state outputs. this pin is associated with lqfp80 and plcc68 packages only. this pin is connected to gnd internally on the lqfp64 package. ior 40 51 52 i input/output read strobe (active low). a high-to-low transition on ior will load the contents of an internal register de?ned by address bits a[2:0] onto the sc16c754b data bus (d[7:0]) for access by external cpu. table 2. pin description continued symbol pin type description lqfp64 lqfp80 plcc68
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 8 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos io w 9 11 18 i input/output write strobe (active low). a low-to-high transition on io w will transfer the contents of the data bus (d[7:0]) from the external cpu to an internal register that is de?ned by address bits a[2:0] and csa and csd. n.c. - 1, 2, 20, 21, 22, 27, 40, 41, 42, 60, 61, 62, 80 31 - not connected reset 27 33 37 i reset. this pin will reset the internal registers and all the outputs. the uart transmitter output and the receiver input will be disabled during reset time. reset is an active high input. ria 63 78 8 i ring indicator (active low). these inputs are associated with individual uart channels, a through d. a logic 0 on these pins indicates the modem has received a ringing signal from the telephone line. a low-to-high transition on these input pins generates a modem status interrupt, if enabled. the state of these inputs is re?ected in the modem status register (msr). rib 19 24 28 ric 30 38 42 rid 50 64 62 r tsa 5 7 14 o request to send (active low). these outputs are associated with individual uart channels, a through d. a logic 0 on the r ts pin indicates the transmitter has data ready and waiting to send. writing a logic 1 in the modem control register mcr[1] will set this pin to a logic 0, indicating data is available. after a reset these pins are set to a logic 1. these pins only affect the transmit and receive operations when auto- r ts function is enabled via the enhanced feature register (efr[6]) for hardware ?ow control operation. r tsb 13 15 22 r tsc 36 47 48 r tsd 44 55 56 rxa 62 77 7 i receive data input. these inputs are associated with individual serial channel data to the sc16c754b. during the local loopback mode, these rx input pins are disabled and tx data is connected to the uart rx input internally. rxb 20 25 29 rxc 29 37 41 rxd 51 65 63 rxrd y - 34 38 o receive ready (active low). rxrd y contains the wire-ored status of all four receive channel fifos, rxrdy a to rxrdy d. it goes low when the trigger level has been reached or a time-out interrupt occurs. it goes high when all rx fifos are empty and there is an error in rx fifo. this pin is associated with lqfp80 and plcc68 packages only. txa8 1017o transmit data. these outputs are associated with individual serial transmit channel data from the sc16c754b. during the local loopback mode, the tx output pin is disabled and tx data is internally connected to the uart rx input. txb 10 12 19 txc 39 50 51 txd 41 52 53 txrd y - 35 39 o transmit ready (active low). txrd y contains the wire-ored status of all four transmit channel fifos, txrdy a to txrdy d. it goes low when there are a trigger level number of spaces available. it goes high when all four tx buffers are full. this pin is associated with lqfp80 and plcc68 packages only. table 2. pin description continued symbol pin type description lqfp64 lqfp80 plcc68
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 9 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6. functional description the sc16c754b uart is pin-compatible with the sc16c554 and sc16c654 uarts. it provides more enhanced features. all additional features are provided through a special enhanced feature register. the uart will perform serial-to-parallel conversion on data characters received from peripheral devices or modems, and parallel-to-parallel conversion on data characters transmitted by the processor. the complete status of each channel of the sc16c754b uart can be read at any time during functional operation by the processor. the sc16c754b can be placed in an alternate mode (fifo mode) relieving the processor of excessive software overhead by buffering received/transmitted characters. both the receiver and transmitter fifos can store up to 64 bytes (including three additional bits of error status per byte for the receiver fifo) and have selectable or programmable trigger levels. primary outputs rxrd y and txrd y allow signalling of dma transfers. the sc16c754b has selectable hardware ?ow control and software ?ow control. hardware ?ow control signi?cantly reduces software overhead and increases system ef?ciency by automatically controlling serial data ?ow using the r ts output and cts input signals. software ?ow control automatically controls data ?ow by using programmable xon/xoff characters. the uart includes a programmable baud rate generator that can divide the timing reference clock input by a divisor between 1 and (2 16 - 1). 6.1 trigger levels the sc16c754b provides independent selectable and programmable trigger levels for both receiver and transmitter dma and interrupt generation. after reset, both transmitter and receiver fifos are disabled and so, in effect, the trigger level is the default value of one byte. the selectable trigger levels are available via the fifo control register (fcr). the programmable trigger levels are available via the trigger level register (tlr). v cc 4, 21, 35, 52 6, 46, 66 13, 47, 64 i power supply input. xtal1 25 31 35 i crystal or external clock input. functions as a crystal input or as an external clock input. a crystal can be connected between xtal1 and xtal2 to form an internal oscillator circuit (see figure 14 ). alternatively, an external clock can be connected to this pin to provide custom data rates. xtal2 26 32 36 o output of the crystal oscillator or buffered clock (see also xtal1). xtal2 is used as a crystal oscillator output or a buffered clock output. table 2. pin description continued symbol pin type description lqfp64 lqfp80 plcc68
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 10 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.2 hardware ?ow control hardware ?ow control is comprised of auto- cts and auto- r ts. auto- cts and auto- r ts can be enabled/disabled independently by programming efr[7:6]. with auto- cts, cts must be active before the uart can transmit data. auto- r ts only activates the r ts output when there is enough room in the fifo to receive data and de-activates the r ts output when the rx fifo is suf?ciently full. the halt and resume trigger levels in the tcr determine the levels at which r ts is activated/deactivated. if both auto- cts and auto- r ts are enabled, when r ts is connected to cts, data transmission does not occur unless the receiver fifo has empty space. thus, overrun errors are eliminated during hardware ?ow control. if not enabled, overrun errors occur if the transmit data rate exceeds the receive fifo servicing latency. fig 5. auto?ow control (auto- r ts and auto- cts) example rx fifo flow control tx fifo parallel to serial tx fifo rx fifo uart 1 uart 2 d7 to d0 rx tx rts cts tx rx cts rts d7 to d0 002aaa228 serial to parallel serial to parallel flow control flow control flow control parallel to serial
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 11 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.2.1 auto- r ts auto- r ts data ?ow control originates in the receiver block (see figure 1 bloc k diag r am of sc16c754b ). figure 6 shows r ts functional timing. the receiver fifo trigger levels used in auto- r ts are stored in the tcr. r ts is active if the rx fifo level is below the halt trigger level in tcr[3:0]. when the receiver fifo halt trigger level is reached, r ts is de-asserted. the sending device (for example, another uart) may send an additional byte after the trigger level is reached (assuming the sending uart has another byte to send) because it may not recognize the de-assertion of r ts until it has begun sending the additional byte. r ts is automatically reasserted once the receiver fifo reaches the resume trigger level programmed via tcr[7:4]. this re-assertion allows the sending device to resume transmission. 6.2.2 auto- cts the transmitter circuitry checks cts before sending the next data byte. when cts is active, the transmitter sends the next byte. to stop the transmitter from sending the following byte, cts must be de-asserted before the middle of the last stop bit that is currently being sent. the auto- cts function reduces interrupts to the host system. when ?ow control is enabled, cts level changes do not trigger host interrupts because the device automatically controls its own transmitter. without auto- cts, the transmitter sends any data present in the transmit fifo and a receiver overrun error may result. n = receiver fifo trigger level. the two blocks in dashed lines cover the case where an additional byte is sent, as described in section 6.2.1 . fig 6. r ts functional timing start byte n start byte n + 1 start stop stop rx rts ior n n+1 12 002aaa226 when cts is low, the transmitter keeps sending serial data out. when cts goes high before the middle of the last stop bit of the current byte, the transmitter ?nishes sending the current byte, but it does not send the next byte. when cts goes from high to low, the transmitter begins sending data again. fig 7. cts functional timing start byte 0 to 7 stop tx cts 002aaa227 start byte 0 to 7 stop
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 12 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.3 software ?ow control software ?ow control is enabled through the enhanced feature register and the modem control register. different combinations of software ?ow control can be enabled by setting different combinations of efr[3:0]. t ab le 3 shows software ?ow control options. remark: when using software ?ow control, the xon/xoff characters cannot be used for data characters. there are two other enhanced features relating to software ?ow control: ? xon any function (mcr[5]): operation will resume after receiving any character after recognizing the xoff character. it is possible that an xon1 character is recognized as an xon any character, which could cause an xon2 character to be written to the rx fifo. ? special character (efr[5]): incoming data is compared to xoff2. detection of the special character sets the xoff interrupt (iir[4]) but does not halt transmission. the xoff interrupt is cleared by a read of the iir. the special character is transferred to the rx fifo. 6.3.1 rx when software ?ow control operation is enabled, the sc16c754b will compare incoming data with xoff1/xoff2 programmed characters (in certain cases, xoff1 and xoff2 must be received sequentially). when the correct xoff character is received, transmission is halted after completing transmission of the current character. xoff detection also sets iir[4] (if enabled via ier[5]) and causes int to go high. to resume transmission, an xon1/xon2 character must be received (in certain cases xon1 and xon2 must be received sequentially). when the correct xon characters are received, iir[4] is cleared, and the xoff interrupt disappears. table 3. software ?ow control options (efr[3:0]) efr[3] efr[2] efr[1] efr[0] tx, rx software ?ow controls 0 0 x x no transmit ?ow control 1 0 x x transmit xon1, xoff1 0 1 x x transmit xon2, xoff2 1 1 x x transmit xon1, xon2, xoff1, xoff2 x x 0 0 no receive ?ow control x x 1 0 receiver compares xon1, xoff1 x x 0 1 receiver compares xon2, xoff2 1 0 1 1 transmit xon1, xoff1 receiver compares xon1 or xon2, xoff1 or xoff2 0 1 1 1 transmit xon2, xoff2 receiver compares xon1 or xon2, xoff1 or xoff2 1 1 1 1 transmit xon1, xon2, xoff1, xoff2 receiver compares xon1 and xon2, xoff1 and xoff2 0 0 1 1 no transmit ?ow control receiver compares xon1 and xon2, xoff1 and xoff2
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 13 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.3.2 tx xoff1/xoff2 character is transmitted when the rx fifo has passed the halt trigger level programmed in tcr[3:0]. xon1/xon2 character is transmitted when the rx fifo reaches the resume trigger level programmed in tcr[7:4]. the transmission of xoff/xon(s) follows the exact same protocol as transmission of an ordinary byte from the fifo. this means that even if the word length is set to be 5, 6, or 7 characters, then the 5, 6, or 7 least signi?cant bits of xoff1/xoff2 and xon1/xon2 will be transmitted. (note that the transmission of 5, 6, or 7 bits of a character is seldom done, but this functionality is included to maintain compatibility with earlier designs.) it is assumed that software ?ow control and hardware ?ow control will never be enabled simultaneously. figure 8 shows an example of software ?ow control. 6.3.3 software ?ow control example 6.3.3.1 assumptions uart1 is transmitting a large text ?le to uart2. both uarts are using software ?ow control with single character xoff (0fh) and xon (0dh) tokens. both have xoff threshold (tcr[3:0] = f) set to 60, and xon threshold (tcr[7:4] = 8) set to 32. both have the interrupt receive threshold (tlr[7:4] = d) set to 52. fig 8. software ?ow control example transmit fifo parallel-to-serial serial-to-parallel xon1 word xon2 word xoff1 word xoff2 word receive fifo parallel-to-serial serial-to-parallel xon1 word xon2 word xoff1 word xoff2 word uart2 uart1 002aaa229 data xoffCxonCxoff compare programmed xon-xoff characters
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 14 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos uart1 begins transmission and sends 52 characters, at which point uart2 will generate an interrupt to its processor to service the rx fifo, but assumes the interrupt latency is fairly long. uart1 will continue sending characters until a total of 60 characters have been sent. at this time, uart2 will transmit a 0fh to uart1, informing uart1 to halt transmission. uart1 will likely send the 61 st character while uart2 is sending the xoff character. now uart2 is serviced and the processor reads enough data out of the rx fifo that the level drops to 32. uart2 will now send a 0dh to uart1, informing uart1 to resume transmission. 6.4 reset t ab le 4 summarizes the state of register after reset. remark: registers dll, dlm, spr, xon1, xon2, xoff1, xoff2 are not reset by the top-level reset signal reset, that is, they hold their initialization values during reset. t ab le 5 summarizes the state of registers after reset. table 4. register reset functions register reset control reset state interrupt enable register reset all bits cleared interrupt identi?cation register reset bit 0 is set; all other bits cleared fifo control register reset all bits cleared line control register reset reset to 0001 1101 (1dh) modem control register reset all bits cleared line status register reset bit 5 and bit 6 set; all other bits cleared modem status register reset bits 3:0 cleared; bits 7:4 input signals enhanced feature register reset all bits cleared receiver holding register reset pointer logic cleared transmitter holding register reset pointer logic cleared transmission control register reset all bits cleared trigger level register reset all bits cleared table 5. signal reset functions signal reset control reset state tx reset high r ts reset high dtr reset high rxrd y reset high txrd y reset low
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 15 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.5 interrupts the sc16c754b has interrupt generation and prioritization (six prioritized levels of interrupts) capability. the interrupt enable register (ier) enables each of the six types of interrupts and the int signal in response to an interrupt generation. the ier can also disable the interrupt system by clearing bits 7:5 and 3:0. when an interrupt is generated, the iir indicates that an interrupt is pending and provides the type of interrupt through iir[5:0]. t ab le 6 summarizes the interrupt control functions. it is important to note that for the framing error, parity error, and break conditions, lsr[7] generates the interrupt. lsr[7] is set when there is an error anywhere in the rx fifo, and is cleared only when there are no more errors remaining in the fifo. lsr[4:2] always represent the error status for the received character at the top of the rx fifo. reading the rx fifo updates lsr[4:2] to the appropriate status for the new character at the top of the fifo. if the rx fifo is empty, then lsr[4:2] are all zeros. for the xoff interrupt, if an xoff ?ow character detection caused the interrupt, the interrupt is cleared by an xon ?ow character detection. if a special character detection caused the interrupt, the interrupt is cleared by a read of the iir. table 6. interrupt control functions iir[5:0] priority level interrupt type interrupt source interrupt reset method 00 0001 none none none none 00 0110 1 receiver line status oe, fe, pe, or bi errors occur in characters in the rx fifo fe, pe, bi: all erroneous characters are read from the rx fifo. oe: read lsr 00 1100 2 rx time-out stale data in rx fifo read rhr 00 0100 2 rhr interrupt drdy (data ready) (fifo disable) rx fifo above trigger level (fifo enable) read rhr 00 0010 3 thr interrupt tfe (thr empty) (fifo disable) tx fifo passes above trigger level (fifo enable) read iir or a write to the thr 00 0000 4 modem status msr[3:0] = 0 read msr 01 0000 5 xoff interrupt receive xoff character(s)/special character receive xon character(s)/read of iir 10 0000 6 cts, rts r ts pin or cts pin change state from active (low) to inactive (high) read iir
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 16 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.5.1 interrupt mode operation in interrupt mode (if any bit of ier[3:0] is 1) the processor is informed of the status of the receiver and transmitter by an interrupt signal, int. therefore, it is not necessary to continuously poll the line status register (lsr) to see if any interrupt needs to be serviced. figure 9 shows interrupt mode operation. 6.5.2 polled mode operation in polled mode (ier[3:0] = 0000) the status of the receiver and transmitter can be checked by polling the line status register (lsr). this mode is an alternative to the fifo interrupt mode of operation where the status of the receiver and transmitter is automatically known by means of interrupts sent to the cpu. figure 10 shows fifo polled mode operation. fig 9. interrupt mode operation 11 11 iir ier thr rhr processor iow / ior int 002aaa230 fig 10. fifo polled mode operation 00 00 lsr ier thr rhr processor iow / ior 002aaa231
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 17 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.6 dma operation there are two modes of dma operation, dma mode 0 or dma mode 1, selected by fcr[3]. in dma mode 0 or fifo disable (fcr[0] = 0) dma occurs in single character transfers. in dma mode 1, multi-character (or block) dma transfers are managed to relieve the processor for longer periods of time. 6.6.1 single dma transfers (dma mode 0/fifo disable) figure 11 shows txrd y and rxrd y in dma mode 0/fifo disable. 6.6.1.1 transmitter when empty, the txrd y signal becomes active. txrd y will go inactive after one character has been loaded into it. 6.6.1.2 receiver rxrd y is active when there is at least one character in the fifo. it becomes inactive when the receiver is empty. fig 11. txrd y and rxrd y in dma mode 0/fifo disable tx wrptr wrptr fifo empty txrdy rx rdptr rdptr fifo empty rxrdy rxrdy 002aaa232 at least one location filled at least one location filled txrdy
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 18 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.6.2 block dma transfers (dma mode 1) figure 12 shows txrd y and rxrd y in dma mode 1. 6.6.2.1 transmitter txrd y is active when there is a trigger level number of spaces available. it becomes inactive when the fifo is full. 6.6.2.2 receiver rxrd y becomes active when the trigger level has been reached, or when a time-out interrupt occurs. it will go inactive when the fifo is empty or an error in the rx fifo is ?agged by lsr[7]. 6.7 sleep mode sleep mode is an enhanced feature of the sc16c754b uart. it is enabled when efr[4], the enhanced functions bit, is set and when ier[4] is set. sleep mode is entered when: ? the serial data input line, rx, is idle (see section 6.8 break and time-out conditions ). ? the tx fifo and tx shift register are empty. ? there are no interrupts pending except thr and time-out interrupts. remark: sleep mode will not be entered if there is data in the rx fifo. in sleep mode, the uart clock and baud rate clock are stopped. since most registers are clocked using these clocks, the power consumption is greatly reduced. the uart will wake up when any change is detected on the rx line, when there is any change in the state of the modem input pins, or if data is written to the tx fifo. remark: writing to the divisor latches, dll and dlm, to set the baud clock, must not be done during sleep mode. therefore, it is advisable to disable sleep mode using ier[4] before writing to dll or dlm. fig 12. txrd y and rxrd y in dma mode 1 tx wrptr wrptr txrdy fifo full txrdy rx rdptr rdptr fifo empty rxrdy rxrdy 002aaa869 trigger level trigger level
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 19 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 6.8 break and time-out conditions an rx idle condition is detected when the receiver line, rx, has been high for 4 character time. the receiver line is sampled midway through each bit. when a break condition occurs, the tx line is pulled low. a break condition is activated by setting lcr[6]. 6.9 programmable baud rate generator the sc16c754b uart contains a programmable baud generator that takes any clock input and divides it by a divisor in the range between 1 and (2 16 - 1). an additional divide-by-4 prescaler is also available and can be selected by mcr[7], as shown in figure 13 . the output frequency of the baud rate generator is 16 the baud rate. the formula for the divisor is given in equation 1 : (1) where: prescaler = 1, when mcr[7] is set to 0 after reset (divide-by-1 clock selected) prescaler = 4, when mcr[7] is set to 1 after reset (divide-by-4 clock selected). remark: the default value of prescaler after reset is divide-by-1. figure 13 shows the internal prescaler and baud rate generator circuitry. dll and dlm must be written to in order to program the baud rate. dll and dlm are the least signi?cant and most signi?cant byte of the baud rate divisor. if dll and dlm are both zero, the uart is effectively disabled, as no baud clock will be generated. remark: the programmable baud rate generator is provided to select both the transmit and receive clock rates. t ab le 7 and t ab le 8 show the baud rate and divisor correlation for crystal with frequency 1.8432 mhz and 3.072 mhz, respectively. figure 14 shows the crystal clock circuit reference. fig 13. prescaler and baud rate generator block diagram divisor xtal1 crystal input frequency prescaler ------------------------------------------------------------------------------------ - ? ?? desired baud rate 16 () ------------------------------------------------------------------------------------------ = baud rate generator logic mcr[7] = 1 mcr[7] = 0 prescaler logic (divide-by-1) internal oscillator logic 002aaa233 xtal1 xtal2 input clock prescaler logic (divide-by-4) reference clock internal baud rate clock for transmitter and receiver
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 20 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos table 7. baud rates using a 1.8432 mhz crystal desired baud rate divisor used to generate 16 clock percent error difference between desired and actual 50 2304 75 1536 110 1047 0.026 134.5 857 0.058 150 768 300 384 600 192 1200 96 1800 64 2000 58 0.69 2400 48 3600 32 4800 24 7200 16 9600 12 19200 6 38400 3 56000 2 2.86 table 8. baud rates using a 3.072 mhz crystal desired baud rate divisor used to generate 16 clock percent error difference between desired and actual 50 3840 75 2560 110 1745 0.026 134.5 1428 0.034 150 1280 300 640 600 320 1200 160 1800 107 0.312 2000 96 2400 80 3600 53 0.628 4800 40 7200 27 1.23 9600 20 19200 10 38400 5
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 21 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7. register descriptions each register is selected using address lines a0, a1, a2, and in some cases, bits from other registers. the programming combinations for register selection are shown in t ab le 9 . [1] mcr[7] can only be modi?ed when efr[4] is set. [2] accessed by a combination of address pins and register bits. [3] accessible only when lcr[7] is logic 1. [4] accessible only when lcr is set to 1011 1111 (bfh). [5] accessible only when efr[4] = 1 and mcr[6] = 1, that is, efr[4] and mcr[6] are read/write enables. [6] accessible only when csa to csd = 0, mcr[2] = 1, and loopback is disabled (mcr[4] = 0). fig 14. crystal oscillator connection 002aaa870 c2 47 pf xtal1 xtal2 x1 1.8432 mhz c1 22 pf c2 33 pf xtal1 xtal2 1.5 k w x1 1.8432 mhz c1 22 pf table 9. register map - read/write properties a2 a1 a0 read mode write mode 0 0 0 receive holding register (rhr) transmit holding register (thr) 0 0 1 interrupt enable register (ier) interrupt enable register (ier) 0 1 0 interrupt identi?cation register (iir) fifo control register (fcr) 0 1 1 line control register (lcr) line control register (lcr) 1 0 0 modem control register (mcr) [1] modem control register (mcr) [1] 1 0 1 line status register (lsr) not applicable 1 1 0 modem status register (msr) not applicable 1 1 1 scratchpad register (spr) scratchpad register (spr) 0 0 0 divisor latch lsb (dll) [2] [3] divisor latch lsb (dll) [2] [3] 0 0 1 divisor latch msb (dlm) [2] [3] divisor latch msb (dlm) [2] [3] 0 1 0 enhanced feature register (efr) [2] [4] enhanced feature register (efr) [2] [4] 1 0 0 xon1 word [2] [4] xon1 word [2] [4] 1 0 1 xon2 word [2] [4] xon2 word [2] [4] 1 1 0 xoff1 word [2] [4] xoff1 word [2] [4] 1 1 1 xoff2 word [2] [4] xoff2 word [2] [4] 1 1 0 transmission control register (tcr) [2] [5] transmission control register (tcr) [2] [5] 1 1 1 trigger level register (tlr) [2] [5] trigger level register (tlr) [2] [5] 1 1 1 fifo ready register [2] [6]
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 22 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos t ab le 10 lists and describes the sc16c754b internal registers. [1] these registers are accessible only when lcr[7] = 0. [2] this bit can only be modi?ed if register bit efr[4] is enabled, that is, if enhanced functions are enabled. [3] the special register set is accessible only when lcr[7] is set to a logic 1. [4] enhanced feature register; xon1/xon2 and xoff1/xoff2 are accessible only when lcr is set to bfh. table 10. sc16c754b internal registers a2 a1 a0 register bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 read/ write general register set [1] 0 0 0 rhr bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r 0 0 0 thr bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 w 0 0 1 ier 0/ cts interrupt enable [2] 0/ r ts interrupt enable [2] 0/ xoff [2] 0/x sleep mode [2] modem status interrupt receive line status interrupt thr empty interrupt rx data available interrupt r/w 0 1 0 fcr rx trigger level (msb) rx trigger level (lsb) 0/tx trigger level (msb) [2] 0/tx trigger level (lsb) [2] dma mode select tx fifo reset rx fifo reset fifo enable w 0 1 0 iir fcr[0] fcr[0] 0/ cts, r ts 0/xoff interrupt priority bit 2 interrupt priority bit 1 interrupt priority bit 0 interrupt status r 0 1 1 lcr dlab break control bit set parity parity type select parity enable number of stop bits word length bit 1 word length bit 0 r/w 1 0 0 mcr 1 or 1 /4 clock [2] tcr and tlr enable [2] 0/xon any [2] 0/enable loopback irq enable op fifo ready enable rts dtr r/w 1 0 1 lsr 0/error in rx fifo thr and tsr empty thr empty break interrupt framing error parity error overrun error data in receiver r 1 1 0 msr cd ri dsr cts d cd d ri d dsr d cts r 1 1 1 spr bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 1 0 tcr bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 1 1 tlr bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 1 1 fifo rdy rx fifo d status rx fifo c status rx fifo b status rx fifo a status tx fifo d status tx fifo c status tx fifo b status tx fifo a status r special register set [3] 0 0 0 dll bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 0 0 1 dlm bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 r/w enhanced register set [4] 0 1 0 efr auto- cts auto- r ts special character detect enable enhanced functions [2] software ?ow control bit 3 software ?ow control bit 2 software ?ow control bit 1 software ?ow control bit 0 r/w 1 0 0 xon1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 0 1 xon2 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 1 0 xoff1 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w 1 1 1 xoff2 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r/w
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 23 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos remark: refer to the notes under t ab le 9 for more register access information. 7.1 receiver holding register (rhr) the receiver section consists of the receiver holding register (rhr) and the receiver shift register (rsr). the rhr is actually a 64-byte fifo. the rsr receives serial data from the rx terminal. the data is converted to parallel data and moved to the rhr. the receiver section is controlled by the line control register (lcr). if the fifo is disabled, location zero of the fifo is used to store the characters. remark: in this case, characters are overwritten if over?ow occurs. if over?ow occurs, characters are lost. the rhr also stores the error status bits associated with each character. 7.2 transmit holding register (thr) the transmitter section consists of the transmit holding register (thr) and the transmit shift register (tsr). the thr is actually a 64-byte fifo. the thr receives data and shifts it into the tsr, where it is converted to serial data and moved out on the tx terminal. if the fifo is disabled, the fifo is still used to store the byte. characters are lost if over?ow occurs.
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 24 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.3 fifo control register (fcr) this is a write-only register that is used for enabling the fifos, clearing the fifos, setting transmitter and receiver trigger levels, and selecting the type of dma signalling. t ab le 11 shows fifo control register bit settings. table 11. fifo control register bits description bit symbol description 7:6 fcr[7] (msb), fcr[6] (lsb) rx trigger. sets the trigger level for the rx fifo. 00 8 characters 01 16 characters 10 56 characters 11 60 characters 5:4 fcr[5] (msb), fcr[4] (lsb) tx trigger. sets the trigger level for the tx fifo. 00 8 spaces 01 16 spaces 10 32 spaces 11 56 spaces fcr[5:4] can only be modi?ed and enabled when efr[4] is set. this is because the transmit trigger level is regarded as an enhanced function. 3 fcr[3] dma mode select. logic 0 = set dma mode 0 logic 1 = set dma mode 1 2 fcr[2] reset tx fifo. logic 0 = no fifo transmit reset (normal default condition) logic 1 = clears the contents of the transmit fifo and resets the fifo counter logic (the transmit shift register is not cleared or altered). this bit will return to a logic 0 after clearing the fifo. 1 fcr[1] reset rx fifo. logic 0 = no fifo receive reset (normal default condition) logic 1 = clears the contents of the receive fifo and resets the fifo counter logic (the receive shift register is not cleared or altered). this bit will return to a logic 0 after clearing the fifo. 0 fcr[0] fifo enable. logic 0 = disable the transmit and receive fifo (normal default condition) logic 1 = enable the transmit and receive fifo
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 25 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.4 line control register (lcr) this register controls the data communication format. the word length, number of stop bits, and parity type are selected by writing the appropriate bits to the lcr. t ab le 12 shows the line control register bit settings. table 12. line control register bits description bit symbol description 7 lcr[7] divisor latch enable. logic 0 = divisor latch disabled (normal default condition) logic 1 = divisor latch enabled 6 lcr[6] break control bit. when enabled, the break control bit causes a break condition to be transmitted (the tx output is forced to a logic 0 state). this condition exists until disabled by setting lcr[6] to a logic 0. logic 0 = no tx break condition (normal default condition) logic 1 = forces the transmitter output (tx) to a logic 0 to alert the communication terminal to a line break condition 5 lcr[5] set parity. lcr[5] selects the forced parity format (if lcr[3] = 1). logic 0 = parity is not forced (normal default condition) lcr[5] = logic 1 and lcr[4] = logic 0: parity bit is forced to a logic 1 for the transmit and receive data lcr[5] = logic 1 and lcr[4] = logic 1: parity bit is forced to a logic 0 for the transmit and receive data 4 lcr[4] parity type select. logic 0 = odd parity is generated (if lcr[3] = 1) logic 1 = even parity is generated (if lcr[3] = 1) 3 lcr[3] parity enable. logic 0 = no parity (normal default condition) logic 1 = a parity bit is generated during transmission and the receiver checks for received parity 2 lcr[2] number of stop bits. speci?es the number of stop bits. 0 = 1 stop bit (word length = 5, 6, 7, 8) 1 = 1.5 stop bits (word length = 5) 1 = 2 stop bits (word length = 6, 7, 8) 1:0 lcr[1:0] word length bits 1, 0. these two bits specify the word length to be transmitted or received. 00 5 bits 01 6 bits 10 7 bits 11 8 bits
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 26 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.5 line status register (lsr) t ab le 13 shows the line status register bit settings. when the lsr is read, lsr[4:2] re?ect the error bits (bi, fe, pe) of the character at the top of the rx fifo (next character to be read). the lsr[4:2] registers do not physically exist, as the data read from the rx fifo is output directly onto the output data bus, di[4:2], when the lsr is read. therefore, errors in a character are identi?ed by reading the lsr and then reading the rhr. lsr[7] is set when there is an error anywhere in the rx fifo, and is cleared only when there are no more errors remaining in the fifo. reading the lsr does not cause an increment of the rx fifo read pointer. the rx fifo read pointer is incremented by reading the rhr. table 13. line status register bits description bit symbol description 7 lsr[7] fifo data error. logic 0 = no error (normal default condition) logic 1 = at least one parity error, framing error, or break indication is in the receiver fifo. this bit is cleared when no more errors are present in the fifo. 6 lsr[6] thr and tsr empty. this bit is the transmit empty indicator. logic 0 = transmitter hold and shift registers are not empty logic 1 = transmitter hold and shift registers are empty 5 lsr[5] thr empty. this bit is the transmit holding register empty indicator. logic 0 = transmit hold register is not empty logic 1 = transmit hold register is empty. the processor can now load up to 64 bytes of data into the thr if the tx fifo is enabled. 4 lsr[4] break interrupt. logic 0 = no break condition (normal default condition) logic 1 = a break condition occurred and associated byte is 00, that is, rx was low for one character time frame 3 lsr[3] framing error. logic 0 = no framing error in data being read from rx fifo (normal default condition) logic 1 = framing error occurred in data being read from rx fifo, that is, received data did not have a valid stop bit 2 lsr[2] parity error. logic 0 = no parity error (normal default condition) logic 1 = parity error in data being read from rx fifo 1 lsr[1] overrun error. logic 0 = no overrun error (normal default condition) logic 1 = overrun error has occurred 0 lsr[0] data in receiver. logic 0 = no data in receive fifo (normal default condition) logic 1 = at least one character in the rx fifo
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 27 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.6 modem control register (mcr) the mcr controls the interface with the modem, data set, or peripheral device that is emulating the modem. t ab le 14 shows modem control register bit settings. [1] mcr[7:5] can only be modi?ed when efr[4] is set, that is, efr[4] is a write enable. table 14. modem control register bits description bit symbol description 7 mcr[7] [1] clock select. logic 0 = divide-by-1 clock input logic 1 = divide-by-4 clock input 6 mcr[6] [1] tcr and tlr enable. logic 0 = no action logic 1 = enable access to the tcr and tlr registers 5 mcr[5] [1] xon any. logic 0 = disable xon any function logic 1 = enable xon any function 4 mcr[4] enable loopback. logic 0 = normal operating mode logic 1 = enable local loopback mode (internal). in this mode the mcr[3:0] signals are looped back into msr[7:4] and the tx output is looped back to the rx input internally. 3 mcr[3] irq enable op. logic 0 = forces inta to intd outputs to the 3-state mode and op output to high state logic 1 = forces the inta to intd outputs to the active state and op output to low state. in loopback mode, controls msr[7]. 2 mcr[2] fifo ready enable. logic 0 = disable the fifo rdy register logic 1 = enable the fifo rdy register. in loopback mode, controls msr[6]. 1 mcr[1] r ts logic 0 = force r ts output to inactive (high) logic 1 = force r ts output to active (low). in loopback mode, controls msr[4]. if auto- r ts is enabled, the r ts output is controlled by hardware ?ow control. 0 mcr[0] dtr logic 0 = force dtr output to inactive (high) logic 1 = force dtr output to active (low). in loopback mode, controls msr[5].
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 28 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.7 modem status register (msr) this 8-bit register provides information about the current state of the control lines from the modem, data set, or peripheral device to the processor. it also indicates when a control input from the modem changes state. t ab le 15 shows modem status register bit settings per channel. [1] the primary inputs ri, cd, cts, dsr are all active low, but their registered equivalents in the msr and mcr (in loopback) registers are active high. table 15. modem status register bits description bit symbol description 7 msr[7] [1] cd (active high, logic 1). this bit is the complement of the cd input during normal mode. during internal loopback mode, it is equivalent to mcr[3]. 6 msr[6] [1] ri (active high, logic 1). this bit is the complement of the ri input during normal mode. during internal loopback mode, it is equivalent to mcr[2]. 5 msr[5] [1] dsr (active high, logic 1). this bit is the complement of the dsr input during normal mode. during internal loopback mode, it is equivalent mcr[0]. 4 msr[4] [1] cts (active high, logic 1). this bit is the complement of the cts input during normal mode. during internal loopback mode, it is equivalent to mcr[1]. 3 msr[3] d cd. indicates that cd input (or mcr[3] in loopback mode) has changed state. cleared on a read. 2 msr[2] d ri. indicates that ri input (or mcr[2] in loopback mode) has changed state from low to high. cleared on a read. 1 msr[1] d dsr. indicates that dsr input (or mcr[0] in loopback mode) has changed state. cleared on a read. 0 msr[0] d cts. indicates that cts input (or mcr[1] in loopback mode) has changed state. cleared on a read.
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 29 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.8 interrupt enable register (ier) the interrupt enable register (ier) enables each of the six types of interrupt, receiver error, rhr interrupt, thr interrupt, xoff received, or cts/rts change of state from low to high. the int output signal is activated in response to interrupt generation. t ab le 16 shows the interrupt enable register bit settings. [1] ier[7:4] can only be modi?ed if efr[4] is set, that is, efr[4] is a write enable. re-enabling ier[1] will cause a new interrupt if the thr is below the threshold. table 16. interrupt enable register bits description bit symbol description 7 ier[7] [1] cts interrupt enable. logic 0 = disable the cts interrupt (normal default condition) logic 1 = enable the cts interrupt 6 ier[6] [1] r ts interrupt enable. logic 0 = disable the r ts interrupt (normal default condition) logic 1 = enable the r ts interrupt 5 ier[5] [1] xoff interrupt. logic 0 = disable the xoff interrupt (normal default condition) logic 1 = enable the xoff interrupt 4 ier[4] [1] sleep mode. logic 0 = disable sleep mode (normal default condition) logic 1 = enable sleep mode. see section 6.7 sleep mode for details. 3 ier[3] modem status interrupt. logic 0 = disable the modem status register interrupt (normal default condition) logic 1 = enable the modem status register interrupt 2 ier[2] receive line status interrupt. logic 0 = disable the receiver line status interrupt (normal default condition) logic 1 = enable the receiver line status interrupt 1 ier[1] transmit holding register interrupt. logic 0 = disable the thr interrupt (normal default condition) logic 1 = enable the thr interrupt 0 ier[0] receive holding register interrupt. logic 0 = disable the rhr interrupt (normal default condition) logic 1 = enable the rhr interrupt
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 30 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.9 interrupt identi?cation register (iir) the iir is a read-only 8-bit register which provides the source of the interrupt in a prioritized manner. t ab le 17 shows interrupt identi?cation register bit settings. the interrupt priority list is shown in t ab le 18 . table 17. interrupt identi?cation register bits description bit symbol description 7:6 iir[7:6] mirror the contents of fcr[0]. 5 iir[5] r ts/ cts low-to-high change of state. 4 iir[4] 1 = xoff/special character has been detected. 3:1 iir[3:1] 3-bit encoded interrupt. see t ab le 18 . 0 iir[0] interrupt status. logic 0 = an interrupt is pending logic 1 = no interrupt is pending table 18. interrupt priority list priority level iir[5] iir[4] iir[3] iir[2] iir[1] iir[0] source of the interrupt 1 0 0 0 1 1 0 receiver line status error 2 0 0 1 1 0 0 receiver time-out interrupt 2 0 0 0 1 0 0 rhr interrupt 3 0 0 0 0 1 0 thr interrupt 4 0 0 0 0 0 0 modem interrupt 5 0 1 0 0 0 0 received xoff signal/ special character 6 100000 cts, r ts change of state from active (low) to inactive (high)
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 31 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.10 enhanced feature register (efr) this 8-bit register enables or disables the enhanced features of the uart. t ab le 19 shows the enhanced feature register bit settings. 7.11 divisor latches (dll, dlm) these are two 8-bit registers which store the 16-bit divisor for generation of the baud clock in the baud rate generator. dlm stores the most signi?cant part of the divisor. dll stores the least signi?cant part of the divisor. note that dll and dlm can only be written to before sleep mode is enabled, that is, before ier[4] is set. table 19. enhanced feature register bits description bit symbol description 7 efr[7] cts ?ow control enable. logic 0 = cts ?ow control is disabled (normal default condition) logic 1 = cts ?ow control is enabled. transmission will stop when a high signal is detected on the cts pin. 6 efr[6] r ts ?ow control enable. logic 0 = r ts ?ow control is disabled (normal default condition) logic 1 = r ts ?ow control is enabled. the r ts pin goes high when the receiver fifo halt trigger level tcr[3:0] is reached, and goes low when the receiver fifo resume transmission trigger level tcr[7:4] is reached. 5 efr[5] special character detect. logic 0 = special character detect disabled (normal default condition) logic 1 = special character detect enabled. received data is compared with xoff2 data. if a match occurs, the received data is transferred to fifo and iir[4] is set to a logic 1 to indicate a special character has been detected. 4 efr[4] enhanced functions enable bit. logic 0 = disables enhanced functions and writing to ier[7:4], fcr[5:4], mcr[7:5]. logic 1 = enables the enhanced function ier[7:4], fcr[5:4], and mcr[7:5] can be modi?ed, that is, this bit is therefore a write enable. 3:0 efr[3:0] combinations of software ?ow control can be selected by programming these bits. see t ab le 3 softw are ? o w control options (efr[3:0]) .
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 32 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 7.12 transmission control register (tcr) this 8-bit register is used to store the rx fifo threshold levels to stop/start transmission during hardware/software ?ow control. t ab le 20 shows transmission control register bit settings. tcr trigger levels are available from 0 to 60 bytes with a granularity of four. remark: tcr can only be written to when efr[4] = 1 and mcr[6] = 1. the programmer must program the tcr such that tcr[3:0] > tcr[7:4]. there is no built-in hardware check to make sure this condition is met. also, the tcr must be programmed with this condition before auto- r ts or software ?ow control is enabled to avoid spurious operation of the device. 7.13 trigger level register (tlr) this 8-bit register is used to store the transmit and received fifo trigger levels used for dma and interrupt generation. trigger levels from 4 to 60 can be programmed with a granularity of 4. t ab le 21 shows trigger level register bit settings. remark: tlr can only be written to when efr[4] = 1 and mcr[6] = 1. if tlr[3:0] or tlr[7:4] are logic 0, the selectable trigger levels via the fifo control register (fcr) are used for the transmit and receive fifo trigger levels. trigger levels from 4 to 60 bytes are available with a granularity of four. the tlr should be programmed for n 4 , where n is the desired trigger level. 7.14 fifo ready register (fifo rdy) the fifo rdy register provides real-time status of the transmit and receive fifos of both channels. table 20. transmission control register bits description bit symbol description 7:4 tcr[7:4] rx fifo trigger level to resume transmission [(0 to 60) bytes]. 3:0 tcr[3:0] rx fifo trigger level to halt transmission [(0 to 60) bytes]. table 21. trigger level register bits description bit symbol description 7:4 tlr[7:4] rx fifo trigger levels (4 to 60), number of characters available. 3:0 tlr[3:0] tx fifo trigger levels (4 to 60), number of spaces available. table 22. fifo ready register bits description bit symbol description 7:4 fifo rdy[7:4] 0 = there are less than a rx trigger level number of characters in the rx fifo 1 = the rx fifo has more than a rx trigger level number of characters available for reading or a time-out condition has occurred 3:0 fifo rdy[3:0] 0 = there are less than a tx trigger level number of spaces available in the tx fifo 1 = there are at least a tx trigger level number of spaces available in the tx fifo
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 33 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos the fifo ready register is a read-only register that can be accessed when any of the four uarts is selected csa to csd = 0, mcr[2] (fifo rdy enable) is a logic 1, and loopback is disabled. the address is 111. 8. programmers guide the base set of registers that is used during high-speed data transfer have a straightforward access method. the extended function registers require special access bits to be decoded along with the address lines. the following guide will help with programming these registers. note that the descriptions below are for individual register access. some streamlining through interleaving can be obtained when programming all the registers. table 23. register programming guide command actions set baud rate to value1, value2 read lcr (03h), save in temp set lcr (03h) to 80h set dll (00h) to value1 set dlm (01h) to value2 set lcr (03h) to temp set xoff1, xon1 to value1, value2 read lcr (03h), save in temp set lcr (03h) to bfh set xoff1 (06h) to value1 set xon1 (04h) to value2 set lcr (03h) to temp set xoff2, xon2 to value1, value2 read lcr (03h), save in temp set lcr (03h) to bfh set xoff2 (07h) to value1 set xon2 (05h) to value2 set lcr (03h) to temp set software ?ow control mode to value read lcr (03h), save in temp set lcr (03h) to bfh set efr (02h) to value set lcr (03h) to temp set ?ow control threshold to value read lcr (03h), save in temp1 set lcr (03h) to bfh read efr (02h), save in temp2 set efr (02h) to 10h + temp2 set lcr (03h) to 00h read mcr (04h), save in temp3 set mcr (04h) to 40h + temp3 set tcr (06h) to value set mcr (04h) to temp3 set lcr (03h) to bfh set efr (02h) to temp2 set lcr (03h) to temp1
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 34 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos [1] sign here means bit-and. set tx fifo and rx fifo thresholds to value read lcr (03h), save in temp1 set lcr (03h) to bfh read efr (02h), save in temp2 set efr (02h) to 10h + temp2 set lcr (03h) to 00h read mcr (04h), save in temp3 set mcr (04h) to 40h + temp3 set tlr (07h) to value set mcr (04h) to temp3 set lcr (03h) to bfh set efr (02h) to temp2 set lcr (03h) to temp1 read fifo rdy register read mcr (04h), save in temp1 set temp2 = temp1 efh [1] set mcr (04h) = 40h + temp2 read ffr (07h), save in temp2 pass temp2 back to host set mcr (04h) to temp1 set prescaler value to divide-by-1 read lcr (03h), save in temp1 set lcr (03h) to bfh read efr (02h), save in temp2 set efr (02h) to 10h + temp2 set lcr (03h) to 00h read mcr (04h), save in temp3 set mcr (04h) to temp3 7fh [1] set lcr (03h) to bfh set efr (02h) to temp2 set lcr (03h) to temp1 set prescaler value to divide-by-4 read lcr (03h), save in temp1 set lcr (03h) to bf read efr (02h), save in temp2 set efr (02h) to 10h + temp2 set lcr (03h) to 00h read mcr (04)h, save in temp3 set mcr (04h) to temp3 + 80h set lcr (03)h to bfh set efr (02h) to temp2 set lcr (03h) to temp1 table 23. register programming guide continued command actions
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 35 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 9. limiting values table 24. limiting values in accordance with the absolute maximum rating system (iec 60134). symbol parameter conditions min max unit v cc supply voltage - 7 v v n voltage on any other pin at d7 to d0 gnd - 0.3 v cc + 0.3 v at any input only pin gnd - 0.3 5.3 v t amb ambient temperature operating in free-air - 40 +85 c t stg storage temperature - 65 +150 c
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 36 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 10. static characteristics [1] meets ttl levels, v io(min) = 2 v and v ih(max) = 0.8 v on non-hysteresis inputs. [2] applies for external output buffers. [3] these parameters apply for d7 to d0. [4] these parameters apply for dtra, dtrb, inia, intb, r tsa, r tsb, rxrd y a, rxrd yb, txrd y a, txrd yb, txa, txb. [5] except xtal2, v ol = 1 v typical. [6] these junction temperatures re?ect simulated conditions. absolute maximum junction temperature is 150 c. the customer is responsible for verifying junction temperature. [7] applies to external clock; crystal oscillator max. 24 mhz. [8] measurement condition, normal operation other than sleep mode: v cc = 3.3 v; t amb =25 c. full duplex serial activity on all two serial (uart) channels at the clock frequency speci?ed in the recommended operating conditions with divisor of 1. [9] when using crystal oscillator. the use of an external clock will increase the sleep current. table 25. static characteristics tolerance of v cc 10 %, unless otherwise speci?ed. symbol parameter conditions v cc = 2.5 v v cc = 3.3 v and 5 v unit min typ max min typ max v cc supply voltage v cc - 10 % v cc v cc +10% v cc - 10 % v cc v cc +10% v v i input voltage 0 - v cc 0-v cc v v ih high-level input voltage [1] 1.6 - v cc 2.0 - v cc v v il low-level input voltage [1] - - 0.65 - - 0.8 v v o output voltage [2] 0-v cc 0-v cc v v oh high-level output voltage i oh = - 8ma [3] - - - 2.0 - - v i oh = - 4ma [4] - - - 2.0 - - v i oh = - 800 m a [3] 1.85 - - - - - v i oh = - 400 m a [4] 1.85 - - - - - v v ol low-level output voltage [5] i ol =8ma [3] - - - - - 0.4 v i ol =4ma [4] - - - - - 0.4 v i ol =2ma [3] - - 0.4 - - - v i ol = 1.6 ma [4] - - 0.4 - - - v c i input capacitance - - 18 - - 18 pf t amb ambient temperature operating in free air - 40 +25 +85 - 40 +25 +85 c t j junction temperature [6] 0 25 125 0 25 125 c f (i)xtal1 crystal input frequency [7] - - 50 - - 80 mhz d clock duty cycle - 50 - - 50 - % i cc supply current f = 5 mhz [8] - - 4.5 - - 6 ma i cc(sleep) sleep mode supply current [9] - 200 - - 200 - m a
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 37 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 11. dynamic characteristics table 26. dynamic characteristics t amb = - 40 c to +85 c; tolerance of v cc 10 %, unless otherwise speci?ed. symbol parameter conditions v cc = 2.5 v v cc = 3.3 v v cc = 5.0 v unit min max min max min max t wl pulse width low 10 - 6 - 6 - ns t wh pulse width high 10 - 6 - 6 - ns f xtal oscillator/clock frequency [1] [2] -48-80 80mhz t 6s address set-up time 0 - 0 - 0 - ns t 6h address hold time 0 - 0 - 0 - ns t 7d ior delay from chip select 10 - 10 - 10 - ns t 7w ior strobe width 25 pf load 90 - 26 - 23 - ns t 7h chip select hold time from ior 0-0-0-ns t 9d read cycle delay 25 pf load 20 - 20 - 20 - ns t 12d delay from ior to data 25 pf load - 90 - 26 - 23 ns t 12h data disable time 25 pf load - 15 - 15 - 15 ns t 13d io w delay from chip select 10 - 10 - 10 - ns t 13w io w strobe width 20 - 20 - 15 - ns t 13h chip select hold time from io w 0-0-0-ns t 15d write cycle delay 25 - 25 - 20 - ns t 16s data set-up time 20 - 15 - 15 - ns t 16h data hold time 15 - 5 - 5 - ns t 17d delay from io w to output 25 pf load - 100 - 33 - 29 ns t 18d delay to set interrupt from modem input 25 pf load - 100 - 24 - 23 ns t 19d delay to reset interrupt from ior 25 pf load - 100 - 24 - 23 ns t 20d delay from stop to set interrupt - 1t rclk [3] -1t rclk [3] -1t rclk [3] ns t 21d delay from ior to reset interrupt 25 pf load - 100 - 29 - 28 ns t 22d delay from start to set interrupt - 100 - 45 - 40 ns t 23d delay from io w to transmit start 8t rclk [3] 24t rclk [3] 8t rclk [3] 24t rclk [3] 8t rclk [3] 24t rclk [3] ns t 24d delay from io w to reset interrupt -100-45-40ns t 25d delay from stop to set rxrd y-1t rclk [3] -1t rclk [3] -1t rclk [3] ns t 26d delay from ior to reset rxrd y -100-45-40ns t 27d delay from io w to set txrd y -100-45-40ns t 28d delay from start to reset txrd y-8t rclk [3] -8t rclk [3] -8t rclk [3] ns t reset reset pulse width [4] 200 - 200 - 200 - ns n baud rate divisor 1 (2 16 - 1) 1 (2 16 - 1) 1 (2 16 - 1)
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 38 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos [1] applies to external clock, crystal oscillator max 24 mhz. [2] maximum frequency = [3] rclk is an internal signal derived from divisor latch lsb (dll) and divisor latch msb (dlm) divisor latches. [4] reset pulse must happen when cs, io w, ior signals are inactive. 11.1 timing diagrams 1 t wclk () --------------- fig 15. general write timing data active active valid address 002aaa109 a0 to a2 csx iow d0 to d7 t 16s t 16h t 13d t 13w t 15d t 6h t 13h t 6s fig 16. general read timing data active active valid address 002aaa110 a0 to a2 csx ior d0 to d7 t 12d t 12h t 7d t 7w t 9d t 6h t 7h t 6s
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 39 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 17. modem input/output timing t 17d change of state t 18d t 18d t 19d 002aaa352 t 18d change of state change of state change of state active active active active active active active change of state rts dtr iow cd cts dsr int ior ri fig 18. external clock timing external clock 002aac357 t w(clk) t wl t wh f xtal 1 t wclk () --------------- =
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 40 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 19. receive timing d0 d1 d2 d3 d4 d5 d6 d7 active active 16 baud rate clock 002aaa113 rx int ior t 21d t 20d 5 data bits 6 data bits 7 data bits stop bit parity bit start bit data bits (0 to 7) next data start bit fig 20. receive ready timing in non-fifo mode d0 d1 d2 d3 d4 d5 d6 d7 002aab063 next data start bit stop bit parity bit t 25d rx rxrdy ior active data ready start bit data bits (0 to 7) active t 26d
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 41 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 21. receive ready timing in fifo mode d0 d1 d2 d3 d4 d5 d6 d7 002aab064 first byte that reaches the trigger level stop bit parity bit t 25d rx rxrdy ior active data ready start bit data bits (0 to 7) active t 26d fig 22. transmit timing active transmitter ready active 16 baud rate clock 002aaa116 t 24d int iow active d0 d1 d2 d3 d4 d5 d6 d7 tx 5 data bits 6 data bits 7 data bits stop bit parity bit start bit data bits (0 to 7) next data start bit t 22d t 23d
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 42 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 23. transmit ready timing in non-fifo mode d0 d1 d2 d3 d4 d5 d6 d7 002aab062 stop bit parity bit t 27d tx iow d0 to d7 active transmitter ready start bit data bits (0 to 7) next data start bit byte #1 txrdy t 28d transmitter not ready active fig 24. transmit ready timing in fifo mode (dma mode 1) d0 d1 d2 d3 d4 d5 d6 d7 002aab065 stop bit parity bit t 27d tx iow d0 to d7 start bit data bits (0 to 7) byte #32 txrdy t 28d fifo full active 5 data bits 6 data bits 7 data bits
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 43 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 12. package outline fig 25. package outline sot414-1 (lqfp64) unit a max. a 1 a 2 a 3 b p ce (1) eh e ll p z y w v q references outline version european projection issue date iec jedec jeita mm 1.6 0.15 0.05 1.45 1.35 0.25 0.23 0.13 0.20 0.09 7.1 6.9 0.4 9.15 8.85 0.64 0.36 7 0 o o 0.08 0.08 1 0.2 dimensions (mm are the original dimensions) note 1. plastic or metal protrusions of 0.25 mm maximum per side are not included. 0.75 0.45 sot414-1 136e06 ms-026 00-01-19 03-02-20 d (1) (1) (1) 7.1 6.9 h d 9.15 8.85 e z 0.64 0.36 d b p e q e a 1 a l p detail x l (a ) 3 b 16 c d h b p e h a 2 v m b d z d a z e e v m a x 1 64 49 48 33 32 17 y pin 1 index w m w m 0 2.5 5 mm scale lqfp64: plastic low profile quad flat package; 64 leads; body 7 x 7 x 1.4 mm sot414-1
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 44 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 26. package outline sot315-1 (lqfp80) unit a max. a 1 a 2 a 3 b p ce (1) eh e ll p z y w v q references outline version european projection issue date iec jedec jeita mm 1.6 0.16 0.04 1.5 1.3 0.25 0.27 0.13 0.18 0.12 12.1 11.9 0.5 14.15 13.85 1.45 1.05 7 0 o o 0.15 0.1 0.2 1 dimensions (mm are the original dimensions) note 1. plastic or metal protrusions of 0.25 mm maximum per side are not included. 0.75 0.30 sot315-1 136e15 ms-026 00-01-19 03-02-25 d (1) (1) (1) 12.1 11.9 h d 14.15 13.85 e z 1.45 1.05 d b p e q e a 1 a l p detail x l (a ) 3 b 20 c d h b p e h a 2 v m b d z d a z e e v m a x 1 80 61 60 41 40 21 y pin 1 index w m w m 0 5 10 mm scale lqfp80: plastic low profile quad flat package; 80 leads; body 12 x 12 x 1.4 mm sot315-1
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 45 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos fig 27. package outline sot188-2 (plcc68) references outline version european projection issue date iec jedec jeita note 1. plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included. sot188-2 44 60 68 1 9 10 26 43 27 61 detail x (a ) 3 b p w m a 1 a a 4 l p b 1 b k x y e e b d h e h v m b d z d a z e e v m a pin 1 index 112e10 ms-018 edr-7319 0 5 10 mm scale 99-12-27 01-11-14 plcc68: plastic leaded chip carrier; 68 leads sot188-2 unit b mm 4.57 4.19 0.51 3.3 0.53 0.33 0.021 0.013 1.27 2.16 45 o 0.18 0.1 0.18 dimensions (mm dimensions are derived from the original inch dimensions) 24.33 24.13 25.27 25.02 2.16 0.81 0.66 1.22 1.07 0.180 0.165 0.02 0.13 0.25 0.01 0.05 0.085 0.007 0.004 0.007 1.44 1.02 0.057 0.040 0.958 0.950 24.33 24.13 0.958 0.950 0.995 0.985 25.27 25.02 0.995 0.985 23.62 22.61 0.93 0.89 23.62 22.61 0.93 0.89 0.085 0.032 0.026 0.048 0.042 e e inches d e a a 1 min. a 4 max. b p ey w v d (1) e (1) h d h e z d (1) max. z e (1) max. b 1 k a 3 l p e d e e
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 46 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 13. soldering of smd packages this text provides a very brief insight into a complex technology. a more in-depth account of soldering ics can be found in application note an10365 surface mount re?ow soldering description . 13.1 introduction to soldering soldering is one of the most common methods through which packages are attached to printed circuit boards (pcbs), to form electrical circuits. the soldered joint provides both the mechanical and the electrical connection. there is no single soldering method that is ideal for all ic packages. wave soldering is often preferred when through-hole and surface mount devices (smds) are mixed on one printed wiring board; however, it is not suitable for ?ne pitch smds. re?ow soldering is ideal for the small pitches and high densities that come with increased miniaturization. 13.2 wave and re?ow soldering wave soldering is a joining technology in which the joints are made by solder coming from a standing wave of liquid solder. the wave soldering process is suitable for the following: ? through-hole components ? leaded or leadless smds, which are glued to the surface of the printed circuit board not all smds can be wave soldered. packages with solder balls, and some leadless packages which have solder lands underneath the body, cannot be wave soldered. also, leaded smds with leads having a pitch smaller than ~0.6 mm cannot be wave soldered, due to an increased probability of bridging. the re?ow soldering process involves applying solder paste to a board, followed by component placement and exposure to a temperature pro?le. leaded packages, packages with solder balls, and leadless packages are all re?ow solderable. key characteristics in both wave and re?ow soldering are: ? board speci?cations, including the board ?nish, solder masks and vias ? package footprints, including solder thieves and orientation ? the moisture sensitivity level of the packages ? package placement ? inspection and repair ? lead-free soldering versus snpb soldering 13.3 wave soldering key characteristics in wave soldering are: ? process issues, such as application of adhesive and ?ux, clinching of leads, board transport, the solder wave parameters, and the time during which components are exposed to the wave ? solder bath speci?cations, including temperature and impurities
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 47 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 13.4 re?ow soldering key characteristics in re?ow soldering are: ? lead-free versus snpb soldering; note that a lead-free re?ow process usually leads to higher minimum peak temperatures (see figure 28 ) than a snpb process, thus reducing the process window ? solder paste printing issues including smearing, release, and adjusting the process window for a mix of large and small components on one board ? re?ow temperature pro?le; this pro?le includes preheat, re?ow (in which the board is heated to the peak temperature) and cooling down. it is imperative that the peak temperature is high enough for the solder to make reliable solder joints (a solder paste characteristic). in addition, the peak temperature must be low enough that the packages and/or boards are not damaged. the peak temperature of the package depends on package thickness and volume and is classi?ed in accordance with t ab le 27 and 28 moisture sensitivity precautions, as indicated on the packing, must be respected at all times. studies have shown that small packages reach higher temperatures during re?ow soldering, see figure 28 . table 27. snpb eutectic process (from j-std-020c) package thickness (mm) package re?ow temperature ( c) volume (mm 3 ) < 350 3 350 < 2.5 235 220 3 2.5 220 220 table 28. lead-free process (from j-std-020c) package thickness (mm) package re?ow temperature ( c) volume (mm 3 ) < 350 350 to 2000 > 2000 < 1.6 260 260 260 1.6 to 2.5 260 250 245 > 2.5 250 245 245
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 48 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos for further information on temperature pro?les, refer to application note an10365 surface mount re?ow soldering description . 14. abbreviations msl: moisture sensitivity level fig 28. temperature pro?les for large and small components 001aac844 temperature time minimum peak temperature = minimum soldering temperature maximum peak temperature = msl limit, damage level peak temperature table 29. abbreviations acronym description cpu central processing unit dll divisor latch lsb dlm divisor latch msb dma direct memory access fifo first in, first out lsb least signi?cant bit msb most signi?cant bit ttl transistor-transistor logic uart universal asynchronous receiver/transmitter
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 49 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 15. revision history table 30. revision history document id release date data sheet status change notice supersedes sc16c754b_4 20081006 product data sheet - sc16c754b_3 modi?cations: ? section 2 f eatures , 5 th bullet item re-written; added f ootnote 1 on page 1 ? t ab le 24 limiting v alues : C deleted symbol v i C deleted symbol v o C added symbol v n ? section 7.14 fifo ready register (fifo rdy) , last paragraph: changed from when any of the two uarts is selected... to when any of the four uarts is selected... ? t ab le 26 dynamic char acter istics : added t ab le note [4] and its reference at t reset . sc16c754b_3 20080516 product data sheet - sc16c754b_2 sc16c754b_2 (9397 750 14668) 20050613 product data sheet - sc16c754b_1 sc16c754b_1 (9397 750 13114) 20050127 product data sheet - -
sc16c754b_4 ? nxp b.v. 2008. all rights reserved. product data sheet rev. 04 6 october 2008 50 of 51 nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos 16. legal information 16.1 data sheet status [1] please consult the most recently issued document before initiating or completing a design. [2] the term short data sheet is explained in section de?nitions. [3] the product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple dev ices. the latest product status information is available on the internet at url http://www .nxp .com . 16.2 de?nitions draft the document is a draft version only. the content is still under internal review and subject to formal approval, which may result in modi?cations or additions. nxp semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. short data sheet a short data sheet is an extract from a full data sheet with the same product type number(s) and title. a short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. for detailed and full information see the relevant full data sheet, which is available on request via the local nxp semiconductors sales of?ce. in case of any inconsistency or con?ict with the short data sheet, the full data sheet shall prevail. 16.3 disclaimers general information in this document is believed to be accurate and reliable. however, nxp semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. right to make changes nxp semiconductors reserves the right to make changes to information published in this document, including without limitation speci?cations and product descriptions, at any time and without notice. this document supersedes and replaces all information supplied prior to the publication hereof. suitability for use nxp semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of an nxp semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. nxp semiconductors accepts no liability for inclusion and/or use of nxp semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customers own risk. applications applications that are described herein for any of these products are for illustrative purposes only. nxp semiconductors makes no representation or warranty that such applications will be suitable for the speci?ed use without further testing or modi?cation. limiting values stress above one or more limiting values (as de?ned in the absolute maximum ratings system of iec 60134) may cause permanent damage to the device. limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the characteristics sections of this document is not implied. exposure to limiting values for extended periods may affect device reliability. terms and conditions of sale nxp semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www .nxp .com/pro? le/ter ms , including those pertaining to warranty, intellectual property rights infringement and limitation of liability, unless explicitly otherwise agreed to in writing by nxp semiconductors. in case of any inconsistency or con?ict between information in this document and such terms and conditions, the latter will prevail. no offer to sell or license nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights. 16.4 trademarks notice: all referenced brands, product names, service names and trademarks are the property of their respective owners. 17. contact information for more information, please visit: http://www .nxp.com for sales of?ce addresses, please send an email to: salesad dresses@nxp.com document status [1] [2] product status [3] de?nition objective [short] data sheet development this document contains data from the objective speci?cation for product development. preliminary [short] data sheet quali?cation this document contains data from the preliminary speci?cation. product [short] data sheet production this document contains the product speci?cation.
nxp semiconductors sc16c754b 5 v, 3.3 v and 2.5 v quad uart, 5 mbit/s (max.) with 64-byte fifos ? nxp b.v. 2008. all rights reserved. for more information, please visit: http://www.nxp.com for sales office addresses, please send an email to: salesaddresses@nxp.com date of release: 6 october 2008 document identifier: sc16c754b_4 please be aware that important notices concerning this document and the product(s) described herein, have been included in section legal information. 18. contents 1 general description . . . . . . . . . . . . . . . . . . . . . . 1 2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 ordering information . . . . . . . . . . . . . . . . . . . . . 2 4 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5 pinning information . . . . . . . . . . . . . . . . . . . . . . 4 5.1 pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . 6 6 functional description . . . . . . . . . . . . . . . . . . . 9 6.1 trigger levels. . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.2 hardware ?ow control . . . . . . . . . . . . . . . . . . . 10 6.2.1 auto- r ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.2.2 auto- cts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.3 software ?ow control . . . . . . . . . . . . . . . . . . . 12 6.3.1 rx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.3.2 tx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.3.3 software ?ow control example . . . . . . . . . . . . 13 6.3.3.1 assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.4 reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.5.1 interrupt mode operation . . . . . . . . . . . . . . . . 16 6.5.2 polled mode operation . . . . . . . . . . . . . . . . . . 16 6.6 dma operation . . . . . . . . . . . . . . . . . . . . . . . . 17 6.6.1 single dma transfers (dma mode 0/fifo disable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.6.1.1 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.6.1.2 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.6.2 block dma transfers (dma mode 1). . . . . . . . 18 6.6.2.1 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.6.2.2 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.7 sleep mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.8 break and time-out conditions . . . . . . . . . . . . 19 6.9 programmable baud rate generator . . . . . . . . 19 7 register descriptions . . . . . . . . . . . . . . . . . . . 21 7.1 receiver holding register (rhr). . . . . . . . . . 23 7.2 transmit holding register (thr) . . . . . . . . . . 23 7.3 fifo control register (fcr) . . . . . . . . . . . . . 24 7.4 line control register (lcr) . . . . . . . . . . . . . . 25 7.5 line status register (lsr) . . . . . . . . . . . . . . . 26 7.6 modem control register (mcr) . . . . . . . . . . . 27 7.7 modem status register (msr). . . . . . . . . . . . 28 7.8 interrupt enable register (ier) . . . . . . . . . . . 29 7.9 interrupt identi?cation register (iir). . . . . . . . 30 7.10 enhanced feature register (efr) . . . . . . . . . 31 7.11 divisor latches (dll, dlm). . . . . . . . . . . . . . . 31 7.12 transmission control register (tcr) . . . . . . . 32 7.13 trigger level register (tlr). . . . . . . . . . . . . . 32 7.14 fifo ready register (fifo rdy) . . . . . . . . . . 32 8 programmers guide . . . . . . . . . . . . . . . . . . . . 33 9 limiting values . . . . . . . . . . . . . . . . . . . . . . . . 35 10 static characteristics . . . . . . . . . . . . . . . . . . . 36 11 dynamic characteristics . . . . . . . . . . . . . . . . . 37 11.1 timing diagrams. . . . . . . . . . . . . . . . . . . . . . . 38 12 package outline . . . . . . . . . . . . . . . . . . . . . . . . 43 13 soldering of smd packages . . . . . . . . . . . . . . 46 13.1 introduction to soldering. . . . . . . . . . . . . . . . . 46 13.2 wave and re?ow soldering . . . . . . . . . . . . . . . 46 13.3 wave soldering. . . . . . . . . . . . . . . . . . . . . . . . 46 13.4 re?ow soldering. . . . . . . . . . . . . . . . . . . . . . . 47 14 abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . 48 15 revision history . . . . . . . . . . . . . . . . . . . . . . . 49 16 legal information . . . . . . . . . . . . . . . . . . . . . . 50 16.1 data sheet status . . . . . . . . . . . . . . . . . . . . . . 50 16.2 de?nitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 16.3 disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . 50 16.4 trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . 50 17 contact information . . . . . . . . . . . . . . . . . . . . 50 18 contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

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