? 2000 in?eon technologies corp. ?optoelectronics division ?san jose, ca www.in?eon.com/opto ?1-888-in?eon (1-888-463-4636) osram opto semiconductors gmbh & co. ohg ?regensburg, germany www.osram-os.com ?+49-941-202-7178 1 may 31, 2000-12 an intelligent display also provides internal memory for the four digits. this approach allows the user to asynchronously address one of four digits, and load new data without regard to the led multiplex timing. figure 1 is a block diagram of the DLX3416. the unit consists of four (5x7) led arrays and a single cmos integrated chip. the ic chip contains the column and row drivers, 128 character rom, four word x7 bit random access memory, oscillator for multiplexing, multiplex counter/decoder, cursor memory, address decoder, and miscellaneous control logic. this application note is intended to serve as a design and appli- cation guide for users of the DLX3416 (referred to as 3416 hereafter) alphanumeric intelligent displays. this appnote also covers device electrical description and operation, consider- ations for general circuit design, and interfacing the 3416 to microprocessors. refer to the speci? data sheet and other in?eon / osram appnotes for more details. electrical & mechanical description the internal electronics in these intelligent displays eliminates all the traditional dif?ulties of using multi-digit light emitting displays (segment decoding, drivers, and multiplexing). figure 1. block diagram?lx3416 rows 0 to 6 display columns 0 to 19 display output logic cue row control logic & row drivers row decoder rom 128x35 bit ascii character decode 4480 bits d6 d5 d4 d3 d2 d1 d0 column decoder write address decoder ram memory timing and control logic latches cursor memory bits 0 to 3 address lines 4x7 bit osc 128 counter 7 counter cursor memory 4x1 bit 7 bit ascii code ram read logic column data wr a0 a1 ce1 ce2 ce3 ce4 cu bl 3 2 1 0 applying the DLX3416* intelligent display device appnote 17
? 2000 in neon technologies corp. optoelectronics division san jose, ca appnote 17 www.in neon.com/opto 1-888-in neon (1-888-463-4636) osram opto semiconductors gmbh & co. ohg regensburg, germany www.osram-os.com +49-941-202-7178 2 may 31, 2000-12 packaging packaging consists of a transfer molded nylon lens which also serves as an ?ncapsulation shell?since it covers ?e of the six ?aces.?the assembled and tested substrate (?tf?multi- layer), is placed within the shell and the entire assembly is then ?led with a water clear ic grade epoxy. this yields a very rugged part, which is quite impervious to moisture, shock and vibration. although not ?ermetic,?the device will easily withstand total immersion in water/detergent solutions. figure 2. top view table 1. pin outs pin function pin function 1 ce1 chip enable 10 gnd 2 ce2 chip enable 11 d0 data input 3 clr clear 12 d1 data input 4 cue cursor enable 13 d2 data input 5cu cursor select 14 d3 data input 6wr write 15 d6 data input 7 a1 digit select 16 d5 data input 8 a0 digit select 17 d4 data input 9v cc 18 bl display blank digit 3 digit 2 digit 1 digit 0 table 2. electrical inputs to the 3416 v cc positive supply +5 volts gnd ground d0-d6 data lines the seven data input lines are designed to accept the ?st 64 ascii characters. see fig- ure 3 for dl3416 character set (the dl3416 interprets all unde?ed codes as a blank). see figure 3 for DLX3416 character set. a0, a1 address lines the address determines the digit position to which the data will be written. address order is right to left for positive-true logic. wr write (active low) data and address to be loaded must be present and stable before and after the trailing edge of write. (see dl3416, DLX3416 data sheets for timing information). ce1 , ce2 chip enable (active high) ce3 , ce4 chip enable (active low) determines which device in an array will actu- ally accept data. when either or both chip enable is in the high state, all inputs are inhibited. clr clear (active low) the data ram and cursor ram of the dl 3416 will be cleared when held low for 15 ms. the minimum for the clr is 1 ms for the DLX3416. cue cursor enable activates cursor function. cursor will not be displayed regardless of cursor memory con- tents when cue is low. cu cursor select (active low) this input must be held high to store data in data memory and low to store data into the cursor memory. bl display blank (active low) blanking the entire display may be accom- plished by holding the bl input low?ot a stored function. when bl is released, the stored characters are again displayed. bl can be used for ?shing or dimming.
? 2000 in neon technologies corp. optoelectronics division san jose, ca appnote 17 www.in neon.com/opto 1-888-in neon (1-888-463-4636) osram opto semiconductors gmbh & co. ohg regensburg, germany www.osram-os.com +49-941-202-7178 3 may 31, 2000-12 figure 3. character set?lx3416 clear memory clearing of the entire internal four digit memory may be accomplished by holding the clear line ( clr ) low for one complete internal display multi- plex cycle, 15 ms minimum for dl 3416, 1 ms for DLX3416. less time may leave some data uncleared. clr also clears the cursor memory. display blanking blanking the display may be accomplished by loading a blank, space or illegal code into each digit of the display or by using the ( bl ) display blank input. setting the ( bl ) input low does not affect the contents of either data or cursor memory. a ?shing display can be realized by pulsing ( bl ). operation multiplexed display systems sequentially read and display data from a memory device. in synchronous systems, control circuitry must com- pare the location of data to be read to the location or position of new data to be stored or displayed, i.e., synchronize before a write can be done. this can be slow and cumbersome. data entry in intelligent displays is asynchronous and may be done in any random order. loading data is similar to writing into a ram. each digit has its own memory location and will display until replaced by another code. figure 4. write cycle waveforms ascii code d0 d1 d2 d3 0 0 0 0 0 1 0 0 0 1 0 1 0 0 2 1 1 0 0 3 0 0 1 0 4 1 0 1 0 5 0 1 1 0 6 1 1 1 0 7 0 0 0 1 8 1 0 0 1 9 0 1 0 1 a 1 1 0 1 b 0 0 1 1 c 1 0 1 1 d 0 1 1 1 e 1 1 1 1 f 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 2 3 4 5 6 7 d6 d5 d4 hex notes: 1. high = 1 level. 2. low = 0 level. 3. upon power up, the device will initialize in a random state. t ah t w t as t ds t dh 4 v 2 v 0 v 4 v 2 v 0 v 4 v 2 v 0 v cu,a0,a1 ce1,ce2 wr data 0 6 the waveforms of figure 4 demonstrate the relation- ships of the signals required to generate a write cycle. (check individual data sheet for minimum values). as can be seen from the waveforms, all signals are referenced from the rising or trailing edge of write. cursor the DLX3416 cursor function causes all dots to light at 50% brightness. the cursor can be used to indicate the position in the display of the next character to be entered. the cursor is not a character but overrides the display of a stored character. upon removal of the cursor, the display will again show the character stored in memory. the cursor can be written into any digit position by set- ting the cursor enable (cue) high, setting the digit address (a1, a0), enabling chip enable, (ce1 , ce2 ), cur- sor select (cu ), write (wr ) and data (d0). a high on data line d0 will place a cursor into the position set by the address a0 and a1. conversely, a low on d0 will remove the cursor. the cursor will remain displayed after the cur- sor (cu ) and write (wr ) signals have been removed. during the cursor-write sequence, data lines d1 through d6 are ignored by the 3416. if the user does not wish to utilize the cursor function, the cursor enable (cue) can be tied low to disable the cursor function. a ?shing cursor can be realized by sim- ply pulsing the cue line after cursor data has been stored. general design considerations using positive true logic, address order is from right to left. for left to right address order, use the ?nes com- plement?or simple inversion of the addresses. for systems with only a 6 bit (abbreviated ascii) code format, data line d6 cannot be left open. data d6 must be the complement of data line d5. a ?isplay test?or ?amp test?function can be achieved by simply storing a cursor into all digits. because of the random state of the cursor ram after power up, if the cursor function is to be used, it will be necessary to clear cursors initially to assure that all cur- sor memories contain its zero state. this is easily accomplished with the clr input. when using the 3416 on a separate display board having more than 6 inches of cable length, it may be necessary to buffer all inputs. this is most easily achieved with hex non-inverting buffers such as the 74365. the object is to prevent transient current in the protection diodes. the buffers should be located on the display board near the displays. local power supply bypass capacitors are also needed in many cases. these should be 6 or 10 volt, tantalum type with 10 ? or greater capacitance. low internal resis- tance is important due to current steps which result from the internal multiplexing of the displays. if small wire cables are used, it is good engineering prac- tice to calculate the wire resistance of the ground plus the +5 volt wires. more than 0.1 volt drop, (at 25 ma per
? 2000 in neon technologies corp. optoelectronics division san jose, ca appnote 17 www.in neon.com/opto 1-888-in neon (1-888-463-4636) osram opto semiconductors gmbh & co. ohg regensburg, germany www.osram-os.com +49-941-202-7178 4 may 31, 2000-12 digit worst cast) should be avoided, since this loss is in addition to any inaccuracies or load regulation limitations of the power supply. the 5 volt power supply for the displays should be the same one supplying v cc to all logic devices which drive the display devices. if a separate supply must be used, then local buffers using hex non-inverting gates should be used on all inputs and these buffers should be powered from the display power supply. this precau- tion is to avoid logic inputs higher than display v cc during power up or line transients. figure 5. interfacing the 3416 a general and straightforward interface circuit is shown in figure 6. this scheme can easily interface to ? systems or any other systems which can provide the seven data lines, appropriate address, and control lines. figure 6. general interface circuit h h h h h h h h h blank previous characters normal data entry enable previous stored cursors l h h h h h h h h h h nc nc nc nc nc d d d bl ce1 ce2 cue cu wr clr a 1 a 0 d6 d5 d4 d3 d2 d1 d0 digit digit digit digit see character set loading cursor loading data x h x x l l l l l l l x l l l l l l l l l l h h h h h h h h h h h x x x h l l l l l l l h h h h h h h h h h h x x x x l l h h l h x x x x l h l h l l x x x x h h h h h h x x x x l l l l l l x x x x l l l l l l x x x x l l l l l h x x x x l l l h h l x x x x l h h l l h x x x x h l h l h h x x h x l l l l l l l l l l l l l l l l l l l l l l l l l l h h h h h l l h h h l l l l h l h x h l l l l h l h h h h h h h h h h x x l l h h x l x x x l h l h x l x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x h h h h x l x nc nc nc nc c c c k nc nc nc b b nc b b nc nc a a nc a e e nc nc nc d d nc nc k k nc b b e e e x = don t care nc = no change from previously displayed characters 3 2 1 0 = all dots/segments on at half brightness display decoder display display display vcc gnd d 0 ? 6 a2 a3 ce 7 / cu cue bl clr wr a0 a1 d15 d12 d11 d8 d7 d4 d3 d0 parallel i/o the parallel i/o device of a microprocessor can easily be con- nected to the circuit in figure 6. one eight bit output port can provide the seven input data bits and the cursor (cu). another eight bit output port can contain the address and chip enable information and the other control signals. init: mvi a,80h out control ;control data mode 0 ;load control register cusr: mvi a,00h out port a mvi b, 0fh ;clear cursor data ;load data port ;set character counter cusri :mov a, b call dspwt dcr b jnz cusri mov a, b call dspwt mvi a, ffh out port b ; ;write subroutine ;decrement counter ;digit 0? ; ; ;set data for control ;load control lines disp: lxi h, table ;set table address disp1 mov a, m out port a mov a, b call dspwt inx h inr b mvi a, 10h cmp b jnz disp1 halt ;move table data into accumulator ;load data port ; ;load address and control ;increment table address ;increment counter set # of digits ; ;16 characters? ;end of program dspwt :ori f0h out port c ani 7fh out port c ori f0h out port c ret ;set control bits off ;load control ;set write bit on ;load write ori f0h ;load control table: db db db db db db db db db db db db db db db db ;0c3h ;0c9h ;0d4h ;0d3h ;0c1h ;0d4h ;0ceh ;0c1h ;0c6h ;0a0h ;0d3h ;0d4h ;0c8h ;0c7h ;0c9h ;0cch
? 2000 in neon technologies corp. optoelectronics division san jose, ca appnote 17 www.in neon.com/opto 1-888-in neon (1-888-463-4636) osram opto semiconductors gmbh & co. ohg regensburg, germany www.osram-os.com +49-941-202-7178 5 may 31, 2000-12 figure 7. 16-digit parallel i/o system figure 8. mapped interface. figure 9. interface with 6800 microprocessor 0-6 7 display port a ce1 wr ce2 d0 display display display ce1 wr ce2 ce1 wr ce2 ce1 wr ce2 d3 d4 d7 d8 d11 d12 d15 port b port c 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 control data 8080 p system 8255 vcc gnd d0 d6 cu clr cue bl a 0 a 1 a 2 a 3 3 2 1 0 wr a b c d 7442 5 / address dis play select decoder parallel i/0 device optional buffers reset int hold wait display display display display 8980 z80 6502 d15 d0 osc a 0 a 1 a 2 a 3 data 0-6 data control cue clr bl wr address data control data address dbe decoder 6820 pia cue bl clr data address h 1 h 2 0 1 0 2 clock driver 6800 ba vma r/w ce ce reset nmi halt irq tsc a 0 a 1 d 0 d 7 display display display display data d15 d0 w figure 7 illustrates a 16 character display with an 8080 system using the 8255 programmable peripheral interface i/o device. the following program will display a simple 16 character mes- sage using this interface. i/o or memory mapped addressing some designers may wish to avoid the additional cost of a par- allel i/o in their system. structuring the addressing architecture for the 3416 to look like a set of peripheral or output devices (i/o mapped) or ram s and rom s (memory mapped) is very easy. figure 8 shows the simplicity of interfacing to micropro- cessors, such as 8080, z80 and 6502 as examples. the interface with the 6800 microprocessor in figure 9 illus- trates the need for designers to check the timing requirements of the 3416 and the ?. the typical data output hold time is only 30 ns for dbe= ? 2 timing; two inverters in the dbe line are added to increase the data output hold time for compatibility with the 50 ns minimum speci?ation of the 3416. conclusion note that although other manufacturers?products are used in examples, this application note does not imply speci? endorsement, or recommendation or warranty of other manu- facturer s products by in?eon / osram. the interface schemes shown demonstrate the simplicity of using the 3416 with microprocessors. the slight differences encountered with various microprocessors to interface with the 3416 are similar to those encountered when using different rams. the techniques used in the examples were shown for their generality, and any display of this family are interchange- able in these examples. the user will undoubtedly invent other schemes to optimize his particular system to its requirements.
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