LOGIC DIAGRAM

WRITE FUNCTION TABLE

WRITE INPUTS

WORDS

WB

WA

WE

0

1

2

3

L

L

L

Q = D

Q0Q0Q0

LHL

Q0

Q = D

Q0

Q0

HL

L

Q0

Q0

Q = D

Q0

H

H

L

Q0Q0Q0

Q = D

X

X

H

Q0

Q0

Q0

Q0

READ FUNCTION TABLE

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

Z

ZZZ

Notes: 1 *: DON’T CARE Z: HIGH IMPEDANCE

2 (Q = D) = THE FOUR SELECT INTERNAL FLIP FLOP OUTPUTS WILL ASSUME THE STATES APPLIED TO THE FOUR

EXTERNAL DATA INPUTS.

3 Q0 = THE LEVEL OF Q BEFORE THE INDICATED INPUT CONDITIONS WERE ESTABLISHED.

4 W0B1 = THE FIRST BIT OF WORD 0, ETC.

M54/M74HC670

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