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Details, datasheet, quote on part number:SN74ALS870DW
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Datasheet text preview:
SN74ALS870 DUAL 16-BY-4 REGISTER FILES
SDAS139A DECEMBER 1982 REVISED JANUARY 1995
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3-State Buffer-Type Outputs Drive Bus Lines Directly Each Register File Has Individual Write-Enable Controls and Address Lines Designed Specifically for Multibus Architecture and Overlapping File Operations Prioritized B-Input Port Prevents Write Conflicts During Dual-Input Mode Package Options Include Plastic Small-Outline (DW) Packages and Standard Plastic (NT) 300-mil DIPs
DW OR NT PACKAGE (TOP VIEW)
description
S0 1A0 1A1 1A2 1A3 1W S2 DQA1 DQA2 DQA3 DQA4 GND
1 2 3 4 5 6 7 8 9 10 11 12
24 23 22 21 20 19 18 17 16 15 14 13
VC C S1 2A3 2A2 2A1 2A0 2W S3 DQB4 DQB3 DQB2 DQB1
This device features two 16-word by 4-bit register files. Each register file has individual write-enable (1W, 2W) controls and address lines. This device has two 4-bit data I/O ports (DQA1DQA4 and DQB1DQB4). The data I/O ports can output to bus A and bus B, receive input from bus A and bus B, receive input from bus A and output to bus B, or output to bus A and receive input from bus B. To prevent writing conflicts in the dual-input mode, the B-input port takes priority. Two select (S0 and S1) lines control which port has access to which register. S2 determines whether the A ports are in the input or the output modes and S3 does likewise for the B ports. The address lines (1A0 1A3 or 2A0 2A3) are decoded by an internal 1-of-16 decoder to select which register word is to be accessed. All outputs are 3-state buffer-type outputs designed specifically to drive bus lines directly. The SN74ALS870 is characterized for operation from 0°C to 70°C.
FUNCTION TABLE FILE SELECT S0 L H L H L H L H L H L H L H L H S1 L L H H L L H H L L H H L L H H FILE SEL 1R to A, 1R to B 2R to A, 1R to B 1R to A, 2R to B 2R to A, 2R to B A to 1R, 1R to B A to 2R, 1R to B A to 1R, 2R to B A to 2R, 2R to B 1R to A, B to 1R 2R to A, B to 1R 1R to A, B to 2R 2R to A, B to 2R B to 1R A to 2R, B to 1R A to 1R, B to 2R B to 2R H H A in, B in in in L H A out, B in out in H L A in, B out in out L L A out, B out out out S2 INPUT/OUTPUT S3 I/O SEL
PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.
Copyright © 1995, Texas Instruments Incorporated
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
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SN74ALS870 DUAL 16-BY-4 REGISTER FILES
SDAS139A DECEMBER 1982 REVISED JANUARY 1995
logic symbol
1A0 1A1 1A2 1A3 2A0 2A1 2A2 2A3 S0 S1 S2 S3 1W 2W DQA1 8 2 3 4 5 19 20 21 22 1 23 7 17 6 18 3 C0/G10 C1/G11 C2 [A in] EN12 [A out] C3 [B in] EN13 [B out] C4 C5 Z6 MUX 12 8,10 9,10 6 7 DQA2 DQA3 DQA4 9 10 11 2A,0,2(1/3)5D 2A 2A,1,3,5D 6 7 RAM 16 × 1 [REG 1] 1A,0,2(1/3)4D 1A 1A,1,3,4D RAM 16 × 1 [REG 2] Z7 MUX 13 Z8 8 9 Z9 14 15 16 DQB2 DQB3 DQB4 11 11 13 DQB1 2A 0 15 3 0 1A 0 15 0 [REG FILE 16 × 4]
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12.
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POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
SN74ALS870 DUAL 16-BY-4 REGISTER FILES
SDAS139A DECEMBER 1982 REVISED JANUARY 1995
logic diagram (positive logic)
Decoder 2 1A0 3 1A1 4 1A2 5 1A3 1 S0 S1 S2 23 7 BIN/Y 1 0 16 2 15 3 4 Decoder BIN/Y 1 0 2 15 3 4 19 20 21 22 2A0 2A1 2A2 2A3
16
S3 1W 2W
17 6 18 REG1
RAM 16×1
0 A 15 A A,D DQA1 8 REG2
RAM 16×1
13
DQB1
0 A 15 A A,D
16
16
Three Identical Channels Not Shown
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V Input voltage, VI: All inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V I/O ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V Voltage applied to a disabled 3-state output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V Operating free-air temperature range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to 70°C Storage temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65°C to 150°C
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
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