M74HC670

2/11

INPUT AND OUTPUT EQUIVALENT CIRCUIT

PIN DESCRIPTION

WRITE FUNCTION TABLE

READ FUNCTION TABLE

X : Don’t Care

Z : High Impedance

(Q = D) = The four select internal flip-flop outputs will assume the states applied to the four external data inputs.

Q0 = The level of Q before the indicated input conditions were established.

W0B1 = The firs bit of word 0, etc.

PIN No

SYMBOL

NAME AND FUNCTION

5, 4

RA, RB

Read Address Inputs

10, 9, 7, 6

Q1 to Q4

Data Outputs

11

RE

3 - State Output Read

Enable Input

12

WE

Write Enable Input (Active

LOW)

14, 13

WA, WB

Write Address Inputs

15, 1, 2, 3

D1 to D4

Data Inputs

8

GND

Ground (0V)

16

Vcc

Positive Supply Voltage

WRITE INPUTS

WORDS

WB

WA

WE

0123

LLL

Q = D

Q0

Q0

Q0

LHL

Q0

Q = D

Q0

Q0

HL

L

Q0

Q0

Q = D

Q0

HH

L

Q0

Q0

Q0

Q = D

XX

H

Q0

Q0

Q0

Q0

READ INPUTS

OUTPUTS

RB

RA

RE

Q0

Q1

Q2

Q3

L

L

L

W0B1

W0B2

W0B3

W0B4

L

H

L

W1B1

W1B2

W1B3

W1B4

H

L

L

W2B1

W2B2

W2B3

W2B4

H

H

L

W3B1

W3B2

W3B3

W3B4

X

X

H

ZZZZ