74HC646 Datasheet, PDF (4/12 Pages) NXP Semiconductors – Octal bus transceiver/register; 3-state

Philips Semiconductors
Octal bus transceiver/register; 3-state
Product specification
74HC/HCT646
Fig.4 Functional diagram.
FUNCTION TABLE
OE
H
H
L
L
L
L
DIR
X
X
L
L
H
H
INPUTS ⁽¹⁾
CP_AB
H or L
↑
X
X
X
H or L
CP_BA
H or L
↑
X
H or L
X
X
S_AB
X
X
X
X
L
H
S_BA
X
X
L
H
X
X
DATA I/O ⁽²⁾
A₀ to A₇ B₀ to B₇
input
input
output
input
input
output
FUNCTION
isolation
store A and B data
real-time B data to A bus
stored B data to A bus
real-time A data to B bus
stored A data to B bus
Notes
1. H = HIGH voltage level
L = LOW voltage level
X = don’t care
↑ = LOW-to-HIGH level transition
2. The data output functions may be enabled or disabled by various signals at the OE and DIR inputs. Data input
functions are always enabled, i.e., data at the bus inputs will be stored on every LOW-to-HIGH transition on the clock
inputs.
September 1993
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