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HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM WITH INTERRUPT
Features
True Dual-Ported memory cells which allow simultaneous access of the same memory location High-speed access - Commercial: 15/20/25/35/55ns (max.) - Industrial 20/25/35/55ns (max.) Low-power operation - IDT70261S Active: 750mW (typ.) Standby: 5mW (typ.) - IDT70261L Active: 750mW (typ.) Standby: 1mW (typ.) Separate upper-byte and lower-byte control for multiplexed bus compatibility
IDT70261S/L
x
x
x
x
x
x x x
x x x x
x
IDT70261 easily expands data bus width to 32 bits or more using the Master/Slave select when cascading more than one device M/S = H for BUSY output flag on Master, M/S = L for BUSY input on Slave Busy and Interrupt Flags On-chip port arbitration logic Full on-chip hardware support of semaphore signaling between ports Fully asynchronous operation from either port TTL-compatible, single 5V (10%) power supply Available in 100-pin Thin Quad Flatpack Industrial temperature range (-40OC to +85OC) is available for selected speeds
Functional Block Diagram
R/WL UBL R/WR UBR
LBL CEL OEL
LBR CER OER
I/O8L-I/O15L I/O0L-I/O7L BUSYL
(1,2)
I/O Control
I/O Control
I/O8R-I/O15R I/O0R-I/O7R BUSYR(1,2)
A13L A0L
Address Decoder
14
MEMORY ARRAY
14
Address Decoder
A13R A0R
CEL OEL R/WL SEML INTL (2)
NOTES: 1. (MASTER): BUSY is output; (SLAVE): BUSY is input. 2. BUSY and INT outputs are non-tri-stated push-pull.
ARBITRATION INTERRUPT SEMAPHORE LOGIC
CER OER R/W R SEMR INTR(2)
3039 drw 01
M/S
FEBRUARY 2000
1
(c)2000 Integrated Device Technology, Inc. DSC 3039/8
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Description
The IDT70261 is a high-speed 16K x 16 Dual-Port Static RAM. The IDT70261 is designed to be used as a stand-alone Dual-Port RAM or as a combination MASTER/SLAVE Dual-Port RAM for 32-bit-or-more word systems. Using the IDT MASTER/SLAVE Dual-Port RAM approach in 32bit or wider memory system applications results in full-speed, error-free operation without the need for additional discrete logic. This device provides two independent ports with separate control, address, and I/O pins that permit independent, asynchronous access for reads or writes to any location in memory. An automatic power down feature controlled by CE permits the on-chip circuitry of each port to enter a very low standby power mode. Fabricated using IDT's CMOS high-performance technology, these devices typically operate on only 750mW of power. The IDT70261 is packaged in a 100-pin TQFP.
VCC R/WL
I/O9L I/O8L I/O7L I/O6L I/O5L I/O4L I/O3L I/O2L GND I/O1L I/O0L
SEML CEL UBL LBL
N/C N/C N/C N/C I/O10L I/O11L I/O12L I/O13L GND I/O14L I/O15L VCC GND I/O0R I/O1R I/O2R VCC I/O3R I/O4R I/O5R I/O6R N/C N/C N/C N/C
1100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 7675 2 74 3 73 4 72 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 71 70 69 68 67 66
A13L A12L A11L A10L A9L A8L A7L
N/C N/C N/C A6L A5L A4L A3L A2L A1L A0L
65 64 63 62 61 60 59 58 57 56 55 54 53 52
OEL
Index
Pin Configurations(1,2,3)
IDT70261PF PN100-1(4) 100-Pin TQFP Top View(5)
INTL BUSYL BUSYR INTR
A0R A1R A2R A3R A4R A5R N/C N/C N/C
3039 drw 02
GND M/S
51 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
,
OER
I/O7R I/O8R I/O9R I/O10R I/O11R I/O12R I/O13R I/O14R GND I/O15R
SEMR CER UBR LBR
R/WR GND
A13R A12R A11R A10R A9R A8R A7R A6R
NOTES: 1. All VCC pins must be connected to power supply. 2. All GND pins must be connected to ground supply. 3. Package body is approximately 14mm x 14mm x 1.4mm. 4. This package code is used to reference the package diagram. 5. This text does not indicate orientation of the actual part-marking.
Pin Names
Left Port Right Port Names Chip Enable Read/Write Enable Output Enable Address Data Input/Output Semaphore Enable Upper Byte Select Lower Byte Select Interrupt Flag Busy Flag Master or Slave Select Power Ground
3039 tbl 01
CEL
R/WL
CER
R/WR
OEL
A0L - A13L I/O0L - I/O15L
OER
A0R - A13R I/O0R - I/O15R
SEML UBL LBL INTL BUSYL
SEMR UBR LBR INTR BUSYR
M/S VCC GND
6.42 2
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Maximum Operating Temperature and Supply Voltage(1,2)
Grade Commercial Industrial Ambient Temperature 0OC to +70OC -40OC to +85OC GND 0V 0V Vcc 5.0V + 10% 5.0V + 10%
3039 tbl 02
Recommended DC Operating Conditions
Symbol VCC GND VIH VIL Parameter Supply Voltage Ground Input High Voltage Input Low Voltage Min. 4.5 0 2.2 -0.5
(1)
Typ. 5.0 0
____
Max. 5.5 0 6.0
(2)
Unit V V V V
3039 tbl 03
NOTES:
1. This is the parameter TA.
____
0.8
NOTES:
1. VIL > -1.5V for pulse width less than 10ns. 2. VTERM must not exceed Vcc + 10%.
Truth Table I Non-Contention Read/Write Control
Inputs(1) Outputs
CE
H X L L L L L L X
R/W X X L L L H H H X
OE
X X X X X L L L H
UB
X H L H L L H L X
LB
X H H L L H L L X
SEM
H H H H H H H H X
I/O8-15 High-Z High-Z DATAIN High-Z DATAIN DATAOUT High-Z DATAOUT High-Z
I/O0-7 High-Z High-Z High-Z DATAIN DATAIN High-Z DATAOUT DATAOUT High-Z
Mode Deselected: Power-Down Both Bytes Deselected Write to Upper Byte Only Write to Lower Byte Only Write to Both Bytes Read Upper Byte Only Read Lower Byte Only Read Both Bytes Outputs Disabled
3039 tbl 04
NOTE: 1. A0L -- A13L A0R -- A13R.
Truth Table II Semaphore Read/Write Control(1)
Inputs Outputs
CE
H X H X L L
R/W H H
OE
L L X X X X
UB
X H X H L X
LB
X H X H X L
SEM
L L L L L L
I/O8-15 DATAOUT DATAOUT DATAIN DATAIN
______ ______
I/O0-7 DATAOUT DATAOUT DATAIN DATAIN
______ ______
Mode Read Data in Semaphore Flag Read Data in Semaphore Flag Write I/O0 into Semaphore Flag Write I/O0 into Semaphore Flag Not Allowed Not Allowed
3039 tbl 05

X X
NOTE: 1. There are eight semaphore flags written to via I/O0 and read from all I/O's(I/O0 - I/O15). These eight semaphores are addressed by A0 - A2.
3 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Absolute Maximum Ratings(1)
Symbol VTERM(2) Rating Terminal Voltage with Respect to GND Temperature Under Bias Storage Temperature DC Output Current Commercial & Industrial -0.5 to +7.0 Unit
Capacitance(1) (TA = +25C, f = 1.0Mhz)
Symbol CIN
V
Parameter Input Capacitance Output Capacitance
Conditions(2) VIN = 3dV VOUT = 3dV
Max. 9 10
Unit pF pF
3039 tbl 07
COUT
TBIAS TSTG IOUT
-55 to +125 -55 to +125 50
o
C C
o
mA
3039 tbl 06
NOTES: 1. This parameter is determined by device characterization but is not production tested. 2. 3dV represents the interpolated capacitance when the input and output signals switch from 0V to 3V or from 3V to 0V.
NOTES: 1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. 2. VTERM must not exceed Vcc + 10% for more than 25% of the cycle time or 10ns maximum, and is limited to < 20mA for the period of VTERM > Vcc + 10%.
DC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range (VCC = 5.0V 10%)
70261S Symbol |ILI| |ILO| VOL VOH Parameter Input Leakage Current(1) Output Leakage Current Output Low Voltage Output High Voltage Test Conditions VCC = 5.5V, VIN = 0V to VCC Min.
___
70261L Max. 10 10 0.4
___
Min.
___
Max. 5 5 0.4
___
Unit A A V V
3039 tbl 08
CE = VIH, VOUT = 0V to VCC
IOL = 4mA IOH = -4mA
___
___
___
___
2.4
2.4
NOTE: 1. At Vcc < 2.0V, input leakages are undefined.
AC Test Conditions
Input Pulse Levels Input Rise/Fall Times Input Timing Reference Levels Output Reference Levels Output Load GND to 3.0V 3ns 1.5V 1.5V Figures 1 and 2
3039 tbl 09
5V 893 DATAOUT BUSY INT DATAOUT 347 30pF 347
5V 893
5pF*
, 3039 drw 03 3039 drw 04
Figure 1. AC Output Test Load
Figure 2. Output Test Load (for tLZ, tHZ, tWZ, tOW) *Including scope and jig.
6.42 4
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
DC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(1) (VCC = 5.0V 10%)
70261X15 Com'l Only Symbol ICC Parameter Dynamic Operating Current (Both Ports Active) Test Condition Version COM'L IND COM'L IND COM'L S L S L S L S L S L S L S L S L S L S L Typ.(2) 190 190
____ ____
70261X20 Com'l & Ind Typ.(2) 180 180 180 180 30 30 30 30 115 115 115 115 1.0 0.2 1.0 0.2 110 110 110 110 Max. 315 275 355 315 85 60 100 80 210 180 245 210 15 5 30 10 185 160 210 185
70261X25 Com'l & Ind Typ. (2) 170 170 170 170 25 25 25 25 105 105 105 105 1.0 0.2 1.0 0.2 100 100 100 100 Max. 305 265 345 305 85 60 100 80 200 170 230 200 15 5 30 10 170 145 200 175
3039 tbl 10
Max. 325 285
____ ____
Unit mA
CE = VIL, Outputs Open SEM = VIH
f = fMAX
(3)
ISB1
Standby Current (Both Ports - TTL Level Inputs)
CEL = CER = VIH SEMR = SEML = VIH
f = fMAX
(3)
35 35
____ ____
95 70
____ ____
mA
ISB2
Standby Current (One Port - TTL Level Inputs)
CE"A" = VIL and CE"B" = VIH (5)
Active Port Outputs Open, f=fMAX (3) SEMR = SEML = VIH
125 125
____ ____
220 190
____ ____
mA
IND COM'L IND COM'L IND
ISB3
Full Standby Current (Both Ports - All CMOS Level Inputs)
Both Ports CEL and CER > VCC - 0.2V VIN > VCC - 0.2V or VIN < 0.2V, f = 0(4) SEMR = SEML > VCC - 0.2V
1.0 0.2
____ ____
15 5
____ ____
mA
ISB4
Full Standby Current (One Port - All CMOS Level Inputs)
VIN > VCC - 0.2V or VIN < 0.2V Active Port Outputs Open f = fMAX(3)
CE"A" < 0.2V and CE"B" > VCC - 0.2V(5) SEMR = SEML > VCC - 0.2V
120 120
____ ____
195 170
____ ____
mA
70261X35 Com'l & Ind Symbol ICC Parameter Dynamic Operating Current (Both Ports Active) Test Condition Version COM'L IND COM'L IND COM'L IND COM'L IND COM'L IND S L S L S L S L S L S L S L S L S L S L Typ.(2) 160 160 160 160 20 20 20 20 95 95 95 95 1.0 0.2 1.0 0.2 90 90 90 90 Max. 295 255 335 295 85 60 100 80 185 155 215 185 15 5 30 10 160 135 190 165
70261X55 Com'l & Ind Typ. (2) 150 150 150 150 13 13 13 13 85 85 85 85 1.0 0.2 1.0 0.2 80 80 80 80 Max. 270 230 310 270 85 60 100 80 165 135 195 165 15 5 30 10 135 110 175 150 Unit mA mA mA mA mA mA mA mA mA mA
CE = VIL, Outputs Open SEM = VIH
f = fMAX
(3)
ISB1
Standby Current (Both Ports - TTL Level Inputs)
CEL = CER = VIH SEMR = SEML = VIH
f = fMAX(3)
ISB2
Standby Current (One Port - TTL Level Inputs)
CE"A" = VIL and CE"B" = VIH(5)
Active Port Outputs Open, f=fMAX(3) SEMR = SEML = VIH
ISB3
Full Standby Current (Both Ports - All CMOS Level Inputs)
Both Ports CEL and CER > VCC - 0.2V VIN > VCC - 0.2V or VIN < 0.2V, f = 0(4) SEMR = SEML > VCC - 0.2V
ISB4
Full Standby Current (One Port - All CMOS Level Inputs)
VIN > VCC - 0.2V or VIN < 0.2V Active Port Outputs Open f=fMAX(3)
CE"A" < 0.2V and CE"B" > VCC - 0.2V(5) SEMR = SEML > VCC - 0.2V
NOTES: 1. 'X' in part numbers indicates power rating (S or L). 2. VCC = 5V, TA = +25C, and are not production tested. ICCDC = 120mA (Typ.) 3. At f = fMAX, address and control lines (except Output Enable) are cycling at the maximum frequency read cycle of 1/tRC, and using "AC Test Conditions" of input levels of GND to 3V. 4. f = 0 means no address or control lines change. 5. Port "A" may be either left or right port. Port "B" is the opposite from port "A".
3039 tbl 11
5 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
AC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(4)
70261X15 Com'l Only Symbol READ CYCLE tRC tAA tACE tABE tAOE tOH tLZ tHZ tPU tPD tSOP tSAA Read Cycle Time Address Access Time Chip Enable Access Time Byte Enable Access Time
(3) (3)
70261X20 Com'l & Ind Min. Max.
70261X25 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
15
____
____
20
____
____
25
____
____
ns ns ns ns ns ns ns ns ns ns ns ns
3039 tbl 12a
15 15 15 10
____
20 20 20 12
____
25 25 25 13
____
____
____
____
____
____
____
Output Enable Access Time Output Hold from Address Change Output Low-Z Time(1,2) Output High-Z Time
(1,2) (2) (2)
____
____
____
3 3
____
3 3
____
3 3
____
____
____
____
10
____
12
____
15
____
Chip Enable to Power Up Time
0
____
0
____
0
____
Chip Disable to Power Down Time
15
____
20
____
25
____
Semaphore Flag Update Pulse (OE or SEM) Semaphore Address Access Time
10
____
10
____
12
____
15
20
25
70261X35 Com'l & Ind Symbol READ CYCLE tRC tAA tACE tABE tAOE tOH tLZ tHZ tPU tPD tSOP tSAA Read Cycle Time Address Access Time Chip Enable Access Time Byte Enable Access Time
(3) (3)
70261X55 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
35
____
____
55
____
____
ns ns ns ns ns ns ns ns ns ns ns ns
3039 tbl 12b
35 35 35 20
____
55 55 55 30
____
____
____
____
____
Output Enable Access Time Output Hold from Address Change Output Low-Z Time
(1,2) (1,2) (2) (2)
____
____
3 3
____
3 3
____
____
____
Output High-Z Time
15
____
25
____
Chip Enable to Power Up Time
0
____
0
____
Chip Disable to Power Down Time
35
____
50
____
Semaphore Flag Update Pulse (OE or SEM) Semaphore Address Access Time
15
____
15
____
35
55
NOTES: 1. Transition is measured 0mV from Low or High-impedance voltage with Output Test Load (Figure 2). 2. This parameter is guaranteed by device characterization, but is not production tested. 3. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. 4. 'X' in part numbers indicates power rating (S or L).
6.42 6
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Waveform of Read Cycles(5)
tRC ADDR tAA (4) (4) tACE tAOE
(4)
CE OE
tABE
(4)
UB, LB
R/W tLZ (1) DATAOUT VALID DATA
(4) (2)
tOH
tHZ
BUSYOUT
tBDD (3, 4)
3039 drw 05
NOTES: 1. Timing depends on which signal is asserted last, OE, CE, LB, or UB. 2. Timing depends on which signal is de-asserted first CE, OE, LB, or UB. 3. tBDD delay is required only in cases where the opposite port is completing a write operation to the same address location. For simultaneous read operations BUSY has no relation to valid output data. 4. Start of valid data depends on which timing becomes effective last tAOE, tACE, tAA or tBDD. 5. SEM = VIH.
Timing of Power-Up Power-Down
CE
ICC ISB
tPU
50%
tPD
50%
3039 drw 06
,
7 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
AC Electrical Characteristics Over the Operating Temperature and Supply Voltage (5)
70261X15 Com'l Only Symbol WRITE CYCLE tWC tEW tAW tAS tWP tWR tDW tHZ tDH tWZ tOW tSWRD tSPS Write Cycle Time Chip Enable to End-of-Write
(3)
70261X20 Com'l & Ind Min. Max.
70261X25 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
15 12 12 0 12 0 10
____
____
20 15 15 0 15 0 15
____
____
25 20 20 0 20 0 15
____
____
ns ns ns ns ns ns ns ns ns ns ns ns ns
3039 tbl 13a
____
____
____
Address Valid to End-of-Write Address Set-up Time (3) Write Pulse Width Write Recovery Time Data Valid to End-of-Write Output High-Z Time Data Hold Time (4) Write Enable to Output in High-Z(1,2) Output Active from End-of-Write (1,2,4)
(1,2)
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
10
____
12
____
15
____
0
____
0
____
0
____
10
____
12
____
15
____
0 5 5
0 5 5
0 5 5
SEM Flag Write to Read Time SEM Flag Contention Window
____
____
____
____
____
____
70261X35 Com'l & Ind Symbol WRITE CYCLE tWC tEW tAW tAS tWP tWR tDW tHZ tDH tWZ tOW tSWRD tSPS Write Cycle Time Chip Enable to End-of-Write
(3)
70261X55 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
35 30 30 0 25 0 15
____
____
55 45 45 0 40 0 30
____
____
ns ns ns ns ns ns ns ns ns ns ns ns ns
3039 tbl 13b
____
____
Address Valid to End-of-Write Address Set-up Time (3) Write Pulse Width Write Recovery Time Data Valid to End-of-Write Output High-Z Time Data Hold Time (4) Write Enable to Output in High-Z(1,2) Output Active from End-of-Write (1,2,4)
(1,2)
____
____
____
____
____
____
____
____
____
____
15
____
25
____
0
____
0
____
15
____
25
____
0 5 5
0 5 5
SEM Flag Write to Read Time SEM Flag Contention Window
____
____
____
____
NOTES: 1. Transition is measured 0mV from Low or High-impedance voltage with Output Test Load (Figure 2). 2. This parameter is guaranteed by device characterization, but is not production tested. 3. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. Either condition must be valid for the entire tEW time. 4. The specification for tDH must be met by the device supplying write data to the RAM under all operating conditions. Although tDH and tOW values will vary over voltage and temperature, the actual tDH will always be smaller than the actual tOW. 5. 'X' in part numbers indicates power rating (S or L).
6.42 8
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Timing Waveform of Write Cycle No. 1, R/W Controlled Timing(1,5,8)
tWC ADDRESS tHZ
(7)
OE
tAW
CE or SEM
(9)
UB or LB
(9)
tAS (6) R/W tWZ (7) DATAOUT
(4)
tWP
(2)
tWR
(3)
tOW
(4)
tDW DATAIN
tDH
3039 drw 07
Timing Waveform of Write Cycle No. 2, CE, UB, LB Controlled Timing(1,5)
tWC ADDRESS tAW
CE or SEM UB or LB
(9)
tAS (6)
(9)
tEW (2)
tWR (3)
R/W tDW DATAIN
3039 drw 08
tDH
NOTES: 1. R/W or CE or UB and LB = VIH during all address transitions. 2. A write occurs during the overlap (tEW or tWP) of a CE = VIL and a R/W = VIL for memory array writing cycle. 3. tWR is measured from the earlier of CE or R/W (or SEM or R/W) going VIH to the end of write cycle. 4. During this period, the I/O pins are in the output state and input signals must not be applied. 5. If the CE or SEM = VIL transition occurs simultaneously with or after the R/W = VIL transition, the outputs remain in the High-impedance state. 6. Timing depends on which enable signal is asserted last, CE or R/W. 7. This parameter is guaranteed by device characterization, but is not production tested. Transition is measured 0mV from steady state with the Output Test Load (Figure 2). 8. If OE = VIL during R/W controlled write cycle, the write pulse width must be the larger of tWP or (tWZ + tDW) to allow the I/O drivers to turn off and data to be placed on the bus for the required tDW. If OE = VIH during an R/W controlled write cycle, this requirement does not apply and the write pulse can be as short as the specified tWP. 9. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. tEW must be met for either condition.
9 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Timing Waveform of Semaphore Read after Write Timing, Either Side(1)
tSAA A0-A2 VALID ADDRESS tAW SEM tDW DATAIN VALID tAS R/W tSWRD OE
Write Cycle Read Cycle
3039 drw 09
tOH
VALID ADDRESS tACE tSOP DATAOUT VALID(2)
tWR tEW
I/O0 tWP
tDH
tAOE
NOTES: 1. CE = VIH or UB and LB = VIH for the duration of the above timing (both write and read cycle). 2. "DATAOUT VALID" represents all I/O's (I/O0-I/O15) equal to the semaphore value.
Timing Waveform of Semaphore Write Contention(1,3,4)
A0"A"-A2"A" MATCH
SIDE
(2)
"A"
R/W"A"
SEM"A"
tSPS A0"B"-A2"B" MATCH
SIDE
(2)
"B"
R/W"B"
SEM"B"
3039 drw 10
NOTES: 1. DOR = DOL = VIL, CER = CEL = VIH, or both UB & LB = VIH. 2. All timing is the same for left and right ports. Port "A" may be either left or right port. Port "B" is the opposite from port "A". 3. This parameter is measured from R/W"A" or SEM"A" going HIGH to R/W"B" or SEM"B" going HIGH. 4. If tSPS is not satisfied, there is no guarantee which side will be granted the semaphore flag.
6.42 10
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
AC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(6,7)
70261X15 Com'l Only Symbol Parameter Min. Max. 70261X20 Com'l & Ind Min. Max. 70261X25 Com'l & Ind Min. Max. Unit
BUSY TIMING (M/S=VIH)
tBAA tBDA tBAC tBDC tAPS tBDD tWH
BUSY Access Time from Address Match BUSY Disable Time from Address Not Matched BUSY Acce ss Time from Chip Enable Low BUSY Acce ss Time from Chip Enable High
Arbitration Priority Set-up Time (2)
____
15 15 15 15
____
____
20 20 20 17
____
____
20 20 20 17
____
ns ns ns ns ns ns ns
____
____
____
____
____
____
____
____
____
5
____
5
____
5
____
BUSY Disable to Valid Data
Write Hold After BUSY
(5)
(3)
18
____
30
____
30
____
12
15
17
BUSY TIMING (M/S=VIL)
tWB tWH
BUSY Input to Write (4)
Write Hold After BUSY
(5)
0 12
____
0 15
____
0 17
____
ns ns
____
____
____
PORT-TO-PORT DELAY TIMING tWDD tDDD Write Pulse to Data Delay (1) Write Data Valid to Read Data Delay (1)
____
30 25
____
45 30
____
50 35
ns ns
3039 tbl 14a
____
____
____
70261X35 Com'l & Ind Symbol Parameter Min. Max.
70261X55 Com'l & Ind Min. Max. Unit
BUSY TIMING (M/S=VIH)
tBAA tBDA tBAC tBDC tAPS tBDD tWH
BUSY Access Time from Address Match BUSY Disable Time from Address Not Matched BUSY Acce ss Time from Chip Enable Low BUSY Acce ss Time from Chip Enable High
Arbitration Priority Set-up Time (2)
____
20 20 20 20
____
____
45 40 40 35
____
ns ns ns ns ns ns ns
____
____
____
____
____
____
5
____
5
____
BUSY Disable to Valid Data(3)
Write Hold After BUSY
(5)
35
____
40
____
25
25
BUSY TIMING (M/S=VIL)
tWB tWH
BUSY Input to Write (4)
Write Hold After BUSY
(5)
0 25
____
0 25
____
ns ns
____
____
PORT-TO-PORT DELAY TIMING tWDD tDDD Write Pulse to Data Delay (1) Write Data Valid to Read Data Delay (1)
____
60 45
____
80 65
ns ns
3039 tbl 14b
____
____
NOTES: 1. Port-to-port delay through RAM cells from writing port to reading port, refer to "Timing Wave form of Write with Port-to-Port Read and BUSY (M/S = VIH)". 2. To ensure that the earlier of the two ports wins. 3. tBDD is a calculated parameter and is the greater of 0, tWDD - tWP (actual), or tDDD - tDW (actual). 4. To ensure that the write cycle is inhibited on port "B" during contention on port "A". 5. To ensure that a write cycle is completed on port "B" after contention on port "A". 6. 'X' in part numbers indicates power rating (S or L).
11 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Timing Waveform of Write with Port-to-Port Read and BUSY (M/S = VIH)(2,4,5)
tWC ADDR"A" MATCH tWP R/W"A" tDW DATAIN "A" tAPS ADDR"B" tBAA
(1)
tDH VALID
MATCH tBDA tBDD
BUSY"B"
tWDD DATAOUT "B" tDDD
(3) 3039 drw 11
VALID
NOTES: 1. To ensure that the earlier of the two ports wins. tAPS is ignored for M/S = VIL (SLAVE). 2. CEL = CER = VIL. 3. OE = VIL for the reading port. 4. If M/S = VIL (slave), BUSY is an input. Then for this example BUSY"A" = VIH and BUSY"B" input is shown above. 5. All timing is the same for left and right ports. Port "A" may be either the left or right port. Port "B" is the port opposite from port "A".
Timing Waveform of Write with BUSY (M/S = VIL)
tWP
R/W"A"
tWB
BUSY"B"
(3)
tWH
(1)
R/W"B"
(2) 3039 drw 12
,
NOTES: 1. tWH must be met for both BUSY input (SLAVE) and output (MASTER). 2. BUSY is asserted on port "B" blocking R/W"B", until BUSY"B" goes HIGH. 3. tWB is only for the "SLAVE" version.
6.42 12
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Waveform of BUSY Arbitration Controlled by CE Timing (M/S = VIH)(1)
ADDR"A" and "B" ADDRESSES MATCH
+-"A"
tAPS (2)
+-"B"
tBAC tBDC
3039 drw 13
*75;"B"
Waveform of BUSY Arbitration Cycle Controlled by Address Match Timing (M/S = VIH)(1)
ADDR"A" tAPS ADDR"B" tBAA
(2)
ADDRESS "N"
MATCHING ADDRESS "N" tBDA
3039 drw 14
BUSY"B"
NOTES: 1. All timing is the same for left and right ports. Port "A" may be either the left or right port. Port "B" is the port opposite from port "A". 2. If tAPS is not satisfied, the BUSY signal will be asserted on one side or another but there is no guarantee on which side BUSY will be asserted.
AC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(1)
70261X15 Com'l Only Symbol INTERRUPT TIMING tAS tWR tINS tINR Address Set-up Time Write Recovery Time Interrupt Set Time Interrupt Reset Time 0 0
____ ____ ____
70261X20 Com'l & Ind Min. Max.
70261X25 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
0 0
____
____ ____
0 0
____
____ ____
ns ns ns ns
3039 tbl 15a
15 15
20 20
20 20
____
____
____
70261X35 Com'l & Ind Symbol INTERRUPT TIMING tAS tWR tINS tINR Address Set-up Time Write Recovery Time Interrupt Set Time Interrupt Reset Time 0 0
____ ____ ____ ____
70261X55 Com'l & Ind Min. Max. Unit
Parameter
Min.
Max.
0 0
____ ____
____ ____
ns ns ns ns
3039 tbl 15b
25 25
40 40
NOTES: 1. 'X' in part numbers indicates power rating (S or L).
13 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Waveform of Interrupt Timing(1)
tWC ADDR"A" tAS (3) INTERRUPT SET ADDRESS
(2) (4)
tWR
CE"A"
R/W"A" tINS (3)
INT"B"
3039 drw 15
tRC ADDR"B" tAS (3) INTERRUPT CLEAR ADDRESS
(2)
CE"B"
OE"B"
tINR (3)
INT"B"
3039 drw 16
NOTES: 1. All timing is the same for left and right ports. Port "A" may be either the left or right port. Port "B" is the port opposite from port "A". 2. See Interrupt Truth Table. 3. Timing depends on which enable signal (CE or R/W) is asserted last. 4. Timing depends on which enable signal (CE or R/W) is de-asserted first.
Truth Tables Truth Table III Interrupt Flag(1)
Left Port R/WL L X X X CEL L X X L OEL X X X L A13L-A0L 3FFF X X 3FFE INTL X X L
(3)
Right Port R/WR X X L X CER X L L X OER X L X X A13R-A0R X 3FFF 3FFE X INTR L
(2)
Function Set Right INTR Flag Reset Right INTR Flag Set Left INTL Flag Reset Left INTL Flag
3039 tbl 16
H
(3)
X X
H
(2)
NOTES: 1. Assumes BUSYL = BUSYR =VIH. 2. If BUSYL = VIL, then no change. 3. If BUSYR = VIL, then no change.
6.42 14
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Truth Table IV Address BUSY Arbitration
Inputs Outputs AOL-A13L AOR-A13R NO MATCH MATCH MATCH MATCH
CEL
X H X L
CER
X X H L
BUSYL(1)
H H H (2)
BUSYR(1)
H H H (2)
Function Normal Normal Normal Write Inhibit(3)
3039 tbl 17
NOTES: 1. Pins BUSYL and BUSYR are both outputs when the part is configured as a master. Both are inputs when configured as a slave. BUSY outputs on the IDT70261 are push-pull, not open drain outputs. On slaves the BUSY input internally inhibits writes. 2. "L" if the inputs to the opposite port were stable prior to the address and enable inputs of this port. "H" if the inputs to the opposite port became stable after the address and enable inputs of this port. If tAPS is not met, either BUSYL or BUSYR = LOW will result. BUSYL and BUSYR outputs can not be LOW simultaneously. 3. Writes to the left port are internally ignored when BUSYL outputs are driving LOW regardless of actual logic level on the pin. Writes to the right port are internally ignored when BUSYR outputs are driving LOW regardless of actual logic level on the pin.
Truth Table V Example of Semaphore Procurement Sequence(1,2,3)
Functions No Action Le ft Port Writes "0" to Semaphore Rig ht Port Writes "0" to Semaphore Le ft Port Writes "1" to Semaphore Le ft Port Writes "0" to Semaphore Rig ht Port Writes "1" to Semaphore Le ft Port Writes "1" to Semaphore Rig ht Port Writes "0" to Semaphore Rig ht Port Writes "1" to Semaphore Le ft Port Writes "0" to Semaphore Le ft Port Writes "1" to Semaphore D0 - D15 Left 1 0 0 1 1 0 1 1 1 0 1 D0 - D15 Right 1 1 1 0 0 1 1 0 1 1 1 Semaphore free Left port has semaphore token No change. Right side has no write access to semaphore Right port obtains semaphore token No change. Left port has no write access to semaphore Left port obtains semaphore token Semaphore free Right port has semaphore token Semaphore free Left port has semaphore token Semaphore free
3039 tbl 18
Status
NOTES: 1. This table denotes a sequence of events for only one of the eight semaphores on the IDT70261. 2. There are eight semaphore flags written to via I/O0 and read from all I/O's (I/O0-I/O15). These eight semaphores are addressed by A0 - A2. 3. CE = VIH, SEM = VIL to access the semaphores. Refer to the Semaphore Read/Write Control Truth Table.
Functional Description
The IDT70261 provides two ports with separate control, address and I/O pins that permit independent access for reads or writes to any location in memory. The IDT70261 has an automatic power down feature controlled by CE. The CE controls on-chip power down circuitry that permits the respective port to go into a standby mode when not selected (CE = VIH). When a port is enabled, access to the entire memory array is permitted. (INTL) is asserted when the right port writes to memory location 3FFE (HEX), where a write is defined as CER = R/WR = VIL per Truth Table III. The left port clears the interrupt through access of address location 3FFE when CEL = OEL = VIL, R/W is a "don't care". Likewise, the right port interrupt flag (INTR) is asserted when the left port writes to memory location 3FFF (HEX) and to clear the interrupt flag (INTR), the right port must read the memory location 3FFF. The message (16 bits) at 3FFE or 3FFF is user-defined since it is an addressable SRAM location. If the interrupt function is not used, address locations 3FFE and 3FFF are not used as mail boxes, but as part of the random access memory. Refer to Truth Table III for the interrupt operation.
Interrupts
If the user chooses the interrupt function, a memory location (mail box or message center) is assigned to each port. The left port interrupt flag
15 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Busy Logic
Busy Logic provides a hardware indication that both ports of the RAM have accessed the same location at the same time. It also allows one of the two accesses to proceed and signals the other side that the RAM is "Busy". The BUSY pin can then be used to stall the access until the operation on the other side is completed. If a write operation has been attempted from the side that receives a BUSY indication, the write signal is gated internally to prevent the write from proceeding. The use of BUSY logic is not required or desirable for all applications. In some cases it may be useful to logically OR the BUSY outputs together and use any BUSY indication as an interrupt source to flag the event of an illegal or illogical operation. If the write inhibit function of BUSY logic is not desirable, the BUSY logic can be disabled by placing the part in slave mode with the M/S pin. Once in slave mode the BUSY pin operates solely as a write inhibit input pin. Normal operation can be programmed by tying the BUSY pins high. If desired, unintended write operations can be prevented to a port by tying the BUSY pin for that port low. The BUSY outputs on the IDT 70261 RAM in master mode, are pushpull type outputs and do not require pull up resistors to operate. If these RAMs are being expanded in depth, then the BUSY indication for the resulting array requires the use of an external AND gate.
DECODER
pulse can be initiated with either the R/W signal or the byte enables. Failure to observe this timing can result in a glitched internal write inhibit signal and corrupted data in the slave.
Semaphores
The IDT70261 is an extremely fast Dual-Port 16K x 16 CMOS Static RAM with an additional 8 address locations dedicated to binary semaphore flags. These flags allow either processor on the left or right side of the DualPort RAM to claim a privilege over the other processor for functions defined by the system designer's software. As an example, the semaphore can be used by one processor to inhibit the other from accessing a portion of the Dual-Port RAM or any other shared resource. The Dual-Port RAM features a fast access time, and both ports are completely independent of each other. This means that the activity on the left port in no way slows the access time of the right port. Both ports are identical in function to standard CMOS Static RAM and can be read from, or written to, at the same time with the only possible conflict arising from the simultaneous writing of, or a simultaneous READ/WRITE of, a nonsemaphore location. Semaphores are protected against such ambiguous situations and may be used by the system program to avoid any conflicts in the non-semaphore portion of the Dual-Port RAM. These devices have an automatic power-down feature controlled by CE, the Dual-Port RAM enable, and SEM, the semaphore enable. The CE and SEM pins control on-chip power down circuitry that permits the respective port to go into standby mode when not selected. This is the condition which is shown in Truth Table V where CE and SEM are both HIGH. Systems which can best use the IDT70261 contain multiple processors or controllers and are typically very high-speed systems which are software controlled or software intensive. These systems can benefit from a performance increase offered by the IDT70261's hardware semaphores, which provide a lockout mechanism without requiring complex programming. Software handshaking between processors offers the maximum in system flexibility by permitting shared resources to be allocated in varying configurations. The IDT70261 does not use its semaphore flags to control any resources through hardware, thus allowing the system designer total flexibility in system architecture. An advantage of using semaphores rather than the more common methods of hardware arbitration is that wait states are never incurred in either processor. This can prove to be a major advantage in very highspeed systems.
MASTER Dual Port RAM
CE BUSYR
BUSYL
SLAVE Dual Port RAM
CE BUSYR
BUSYL
BUSYL
MASTER Dual Port RAM BUSYL
CE BUSYR
SLAVE Dual Port RAM
CE BUSYR BUSYR
3039 drw 17
BUSYL
Figure 3. Busy and chip enable routing for both width and depth expansion with IDT70261 RAMs.
Width Expansion with Busy Logic Master/Salve Arrays
When expanding an IDT70261 RAM array in width while using BUSY logic, one master part is used to decide which side of the RAM array will receive a BUSY indication, and to output that indication. Any number of slaves to be addressed in the same address range as the master, use the BUSY signal as a write inhibit signal. Thus on the IDT70261 RAM the BUSY pin is an output if the part is used as a master (M/S pin = VIH), and the BUSY pin is an input if the part used as a slave (M/S pin = VIL) as shown in Figure 3. If two or more master parts were used when expanding in width, a split decision could result with one master indicating BUSY on one side of the array and another master indicating BUSY on one other side of the array. This would inhibit the write operations from one port for part of a word and inhibit the write operations from the other port for the other part of the word. The BUSY arbitration, on a master, is based on the chip enable and address signals only. It ignores whether an access is a read or write. In a master/slave array, both address and chip enable must be valid long enough for a BUSY flag to be output from the master before the actual write
How the Semaphore Flags Work
The semaphore logic is a set of eight latches which are independent of the Dual-Port RAM. These latches can be used to pass a flag, or token, from one port to the other to indicate that a shared resource is in use. The semaphores provide a hardware assist for a use assignment method called "Token Passing Allocation." In this method, the state of a semaphore latch is used as a token indicating that shared resource is in use. If the left processor wants to use this resource, it requests the token by setting the latch. This processor then verifies its success in setting the latch by reading it. If it was successful, it proceeds to assume control over the shared resource. If it was not successful in setting the latch, it determines that the right side processor has set the latch first, has the token and is using the shared resource. The left processor can then either repeatedly request
6.42 16
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
that semaphore's status or remove its request for that semaphore to perform another task and occasionally attempt again to gain control of the token via the set and test sequence. Once the right side has relinquished the token, the left side should succeed in gaining control. The semaphore flags are active low. A token is requested by writing a zero into a semaphore latch and is released when the same side writes a one to that latch. The eight semaphore flags reside within the IDT70261 in a separate memory space from the Dual-Port RAM. This address space is accessed by placing a low input on the SEM pin (which acts as a chip select for the semaphore flags) and using the other control pins (Address, OE, and R/W) as they would be used in accessing a standard Static RAM. Each of the flags has a unique address which can be accessed by either side through address pins A0 - A2. When accessing the semaphores, none of the other address pins has any effect. When writing to a semaphore, only data pin D0 is used. If a low level is written into an unused semaphore location, that flag will be set to a zero on that side and a one on the other side (see Table V). That semaphore can now only be modified by the side showing the zero. When a one is written into the same location from the same side, the flag will be set to a one for both sides (unless a semaphore request from the other side is pending) and then can be written to by both sides. The fact that the side which is able to write a zero into a semaphore subsequently locks out writes from the other side is what makes semaphore flags useful in interprocessor communications. (A thorough discussion on the use of this feature follows shortly.) A zero written into the same location from the other side will be stored in the semaphore request latch for that side until the semaphore is freed by the first side. When a semaphore flag is read, its value is spread into all data bits so that a flag that is a one reads as a one in all data bits and a flag containing a zero reads as all zeros. The read value is latched into one side's output register when that side's semaphore select (SEM) and output enable (OE) signals go active. This serves to disallow the semaphore from changing state in the middle of a read cycle due to a write cycle from the other side. Because of this latch, a repeated read of a semaphore in a test loop must cause either signal (SEM or OE) to go inactive or the output will never change. A sequence WRITE/READ must be used by the semaphore in order to guarantee that no system level contention will occur. A processor requests access to shared resources by attempting to write a zero into a semaphore location. If the semaphore is already in use, the semaphore request latch will contain a zero, yet the semaphore flag will appear as one, a fact which the processor will verify by the subsequent read (see Table V). As an example, assume a processor writes a zero to the left port at a free semaphore location. On a subsequent read, the processor will verify that it has written successfully to that location and will assume control over the resource in question. Meanwhile, if a processor on the right side attempts to write a zero to the same semaphore flag it will fail, as will be verified by the fact that a one will be read from that semaphore on the right side during subsequent read. Had a sequence of READ/WRITE been used instead, system contention problems could have occurred during the gap between the read and write cycles. It is important to note that a failed semaphore request must be followed by either repeated reads or by writing a one into the same location. The reason for this is easily understood by looking at the simple logic diagram of the semaphore flag in Figure 4. Two semaphore request latches feed
into a semaphore flag. Whichever latch is first to present a zero to the semaphore flag will force its side of the semaphore flag LOW and the other side HIGH. This condition will continue until a one is written to the same semaphore request latch. Should the other side's semaphore request latch have been written to a zero in the meantime, the semaphore flag will flip
L PORT SEMAPHORE REQUEST FLIP FLOP D0 WRITE SEMAPHORE READ
D Q
R PORT SEMAPHORE REQUEST FLIP FLOP
Q D
D0 WRITE
SEMAPHORE READ
, 3039 drw 18
Figure 4. IDT70261 Semaphore Logic
over to the other side as soon as a one is written into the first side's request latch. The second side's flag will now stay low until its semaphore request latch is written to a one. From this it is easy to understand that, if a semaphore is requested and the processor which requested it no longer needs the resource, the entire system can hang up until a one is written into that semaphore request latch. The critical case of semaphore timing is when both sides request a single token by attempting to write a zero into it at the same time. The semaphore logic is specially designed to resolve this problem. If simultaneous requests are made, the logic guarantees that only one side receives the token. If one side is earlier than the other in making the request, the first side to make the request will receive the token. If both requests arrive at the same time, the assignment will be arbitrarily made to one port or the other. One caution that should be noted when using semaphores is that semaphores alone do not guarantee that access to a resource is secure. As with any powerful programming technique, if semaphores are misused or misinterpreted, a software error can easily happen. Initialization of the semaphores is not automatic and must be handled via the initialization program at power-up. Since any semaphore request flag which contains a zero must be reset to a one, all semaphores on both sides should have a one written into them at initialization from both sides to assure that they will be free when needed.
Using SemaphoresSome Examples
Perhaps the simplest application of semaphores is their application as resource markers for the IDT70261's Dual-Port RAM. Say the 16K x 16 RAM was to be divided into two 8K x 16 blocks which were to be dedicated at any one time to servicing either the left or right port. Semaphore 0 could be used to indicate the side which would control the lower section of memory, and Semaphore 1 could be defined as the indicator for the upper section of memory. To take a resource, in this example the lower 8K of Dual-Port RAM, the processor on the left port could write and then read a zero in to Semaphore 0. If this task were successfully completed (a zero was read back rather than a one), the left processor would assume control of the lower 8K. Meanwhile the right processor was attempting to gain control
17 6.42
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
of the resource after the left processor, it would read back a one in response to the zero it had attempted to write into Semaphore 0. At this point, the software could choose to try and gain control of the second 8K section by writing, then reading a zero into Semaphore 1. If it succeeded in gaining control, it would lock out the left side. Once the left side was finished with its task, it would write a one to Semaphore 0 and may then try to gain access to Semaphore 1. If Semaphore 1 was still occupied by the right side, the left side could undo its semaphore request and perform other tasks until it was able to write, then read a zero into Semaphore 1. If the right processor performs a similar task with Semaphore 0, this protocol would allow the two processors to swap 8K blocks of Dual-Port RAM with each other. The blocks do not have to be any particular size and can even be variable, depending upon the complexity of the software using the semaphore flags. All eight semaphores could be used to divide the DualPort RAM or other shared resources into eight parts. Semaphores can even be assigned different meanings on different sides rather than being given a common meaning as was shown in the example above. Semaphores are a useful form of arbitration in systems like disk interfaces where the CPU must be locked out of a section of memory during
a transfer and the I/O device cannot tolerate any wait states. With the use of semaphores, once the two devices has determined which memory area was "off-limits" to the CPU, both the CPU and the I/O devices could access their assigned portions of memory continuously without any wait states. Semaphores are also useful in applications where no memory "WAIT" state is available on one or both sides. Once a semaphore handshake has been performed, both processors can access their assigned RAM segments at full speed. Another application is in the area of complex data structures. In this case, block arbitration is very important. For this application one processor may be responsible for building and updating a data structure. The other processor then reads and interprets that data structure. If the interpreting processor reads an incomplete data structure, a major error condition may exist. Therefore, some sort of arbitration must be used between the two different processors. The building processor arbitrates for the block, locks it and then is able to go in and update the data structure. When the update is completed, the data structure block is released. This allows the interpreting processor to come back and read the complete data structure, thereby guaranteeing a consistent data structure.
6.42 18
IDT70261S/L High-Speed 16K x 16 Dual-Port Static RAM with Interrupt
Industrial and Commercial Temperature Ranges
Ordering Information
IDT XXXXX Device Type A Power 999 Speed A Package A Process/ Temperature Range Blank I Commercial (0C to +70C) Industrial (-40C to +85C)
PF
100-pin TQFP (PN100-1)
15 20 25 35 55 S L 70261
Commercial Commercial & Industrial Commercial & Industrial Commercial & Industrial Commercial & Industrial Standard Power Low Power
Speed in nanoseconds
256K (16K x 16) Dual-Port RAM with Interrupt
3039 drw 19
Datasheet Document History
1/14/99: Initiated datasheet document history Converted to new format Cosmetic and typographical corrections Pages 2 Added additional notes to pin configurations Changed drawing format Page 1 Corrected DSC number Added Industrial Temperature Ranges and removed related notes Replaced IDT logo Changed 200mV in table and waveform notes to 0mV
6/4/99: 2/18/00:
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19 6.42
for Tech Support: 831-754-4613 DualPortHelp@idt.com
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