CD74FCT646 Datasheet, PDF (2/8 Pages) Texas Instruments – BiCMOS FCT Interface Logic, Octal Bus Transceiver/Register, Three-State

CD74FCT646
Functional Diagram
A0
4
A1
5
A2
6
A3
7
A DATA PORT
A4
8
A5
9
A6
10
A7
11
21
OE
3
DIR
1
FLIP-FLOP CAB CLOCK
CLOCKS CBA CLOCK
23
20
B0
19
B1
18
B2
17
B3
B DATA PORT
16
B4
15
B5
14
B6
13
B7
2
22
SAB SOURCE
DATA SOURCE
SELECTION
SBA SOURCE _INPUTS
GND = PIN 12
V_CC = PIN 24
TRUTH TABLE (Note 1)
INPUTS
DATA I/O (Note 2)
OPERATION OR FUNCTION
OE
DIR CAB CBA SAB SBA
A0 THRU A7
B0 THRU B7
CD74FCT646
X
X
↑
X
X
X Input
Not Specified
Store A, B Unspecified
X
X
X
↑
X
X Not Specified
Input
Store B, A Unspecified
H
X
↑
↑
X
X Input
H
X H or L H or L X
X
Input
Store A and B Data
Isolation, Hold Storage
L
L
X
X
X
L Output
L
L
X H or L X
H
Input
Real Time B Data to A Bus
Stored B Data to A Bus
L
H
X
X
L
X Input
L
H H or L X
H
X
Output
Real Time A Data to B Bus
Stored A Data to B Bus
NOTES:
1. H= HIGH Voltage Level
L = LOW Voltage Level
↑ = Transition from Low to High
X = Immaterial
2. The data output functions may be enabled or disabled by various signals at the OE and DIR inputs. Data input functions are always en-
abled, i.e., data at the bus pins will be stored on every low to high transition of the clock inputs. To prevent excess currents in the high Z
modes, all I/O terminals should be terminated with 10kΩ resistors.
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