HIT HD74AC670 Datasheet

HD74AC670

4 × 4 Register File with 3-State Output

Description

The HD74AC670 contains 16 high speed, low power, transparent D-type latches arranged as four words of
four bits each, to function as a 4 × 4 register file. Separate read and write inputs, both address and enable,
allow simultaneous read and write operation. The 3-state outputs make it possible to connect up to 128
outputs to increase the word capacity up to 512 words. Any number of these devices can be operated in
parallel to generate an n-bit length.

Features

• 3-State Outputs Drive Bus Lines or Buffer Memory Address Registers

• Outputs Source/Sink 24 mA

Pin Arrangement

D

D3

D4

RA1

RA0

O4

O3

GND

1

2

2

3

4

5

6

7

8

(Top view)

16

15

14

13

12

11

10

CC

V

D1

WA0

WA1

WE

OE

1

O

9

O2

HD74AC670

Logic Symbol

12 15 1 2 3

14
13

WE D

WA0

WA1
5
4

RA0

RA0

OE O1 O2 O3 O4

1 D2 D3 D4

11

10 9 7 6

VCC=Pin 16
GND=Pin 8

Pin Names

D1 to D

4

WA0, WA
WE Write Enable Input (Active Low)
RA0, RA

1

OE 3-State Output Enable Input (Active Low)
O1 to O

4

Data Inputs
Write Address Inputs

1

Read Address Inputs

Data Outputs

Write Function Table

Write Inputs
WE WA

L L L Word 0
L L H Word 1
L H L Word 2
L H H Word 3
H X X None (hold)

H : High Voltage Level
L : Low Voltage Level
X : Immaterial

2

1

WA

0

D Inputs to

Read Function Table

Read Inputs
OE RA

L L L Word 0
L L H Word 1
L H L Word 2
L H H Word 3
H X X None (HIGH Z)

H : High Voltage Level
L : Low Voltage Level
X : Immaterial

1

RA

0

Outputs from

HD74AC670

3