M74HC670 Datasheet, PDF (2/11 Pages) STMicroelectronics – 4 WORD x 4 BIT REGISTER FILE (3 STATE)

M74HC670
INPUT AND OUTPUT EQUIVALENT CIRCUIT
PIN DESCRIPTION
PIN No
5, 4
10, 9, 7, 6
11
12
14, 13
15, 1, 2, 3
8
16
SYMBOL
RA, RB
Q1 to Q4
RE
WE
WA, WB
D1 to D4
GND
Vcc
NAME AND FUNCTION
Read Address Inputs
Data Outputs
3 - State Output Read
Enable Input
Write Enable Input (Active
LOW)
Write Address Inputs
Data Inputs
Ground (0V)
Positive Supply Voltage
WRITE FUNCTION TABLE
WRITE INPUTS
WB
WA
WE
L
L
L
L
H
L
H
L
L
H
H
L
X
X
H
0
Q=D
Q0
Q0
Q0
Q0
WORDS
1
Q0
Q=D
Q0
Q0
Q0
2
Q0
Q0
Q=D
Q0
Q0
READ FUNCTION TABLE
READ INPUTS
OUTPUTS
RB
RA
RE
Q0
Q1
Q2
L
L
L
W0B1
W0B2
W0B3
L
H
L
W1B1
W1B2
W1B3
H
L
L
W2B1
W2B2
W2B3
H
H
L
W3B1
W3B2
W3B3
X
X
H
Z
Z
Z
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.
3
Q0
Q0
Q0
Q=D
Q0
Q3
W0B4
W1B4
W2B4
W3B4
Z
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