CD74FCT653 Datasheet, PDF (3/9 Pages) Texas Instruments – FCT Interface Logic, Octal Bus Transceivers/ Registers, Open Drain (A Side), Three-State (B Side)

CD74FCT653, CD74FCT654
Functional Diagram
A0
4
A1
5
A2
6
A3
7
A DATA PORT
A4
8
A5
9
A6
10
A7
11
21
OEBA
3
OEAB
1
FLIP-FLOP CAB CLOCK ₂₃
CLOCKS CBA CLOCK
20
B0
19
B1
18
B2
17
B3
B DATA PORT
16
B4
15
B5
14
B6
13
B7
2 _{SAB SOURCE} DATA SOURCE
22
SELECTION
SBA SOURCE _INPUTS
GND = PIN 12
V_CC = PIN 24
TRUTH TABLE
INPUTS
DATA I/O
OPERATION OR FUNCTION
OEAB OEBA CAB CBA SAB SBA A0 THRU A7 B0 THRU B7
CD74FCT653
CD74FCT654
L
H H or L H or L X
X Input
L
H
↑
↑
X
X Input
Input
Input
Isolation (Note 1)
Store A and B Data
Isolation (Note 1)
Store A and B Data
X
H
↑ H or L X
X Input
H
H
↑
↑ X (3) X Input
Unspecified (2) Store A, Hold B
Store A, Hold B
Output
Store A in both registers Store A in both registers
L
X H or L ↑
X
X Unspecified (2) Input
L
L
↑
↑
X X (3) Output
Input
Hold A, Store B
Hold A, Store B
Store B in both registers Store B in both registers
L
L
X
X
X
L Output
L
L
X H or L X
H Output
Input
Input
Real-Time B Data to A Bus Real-Time B Data to A Bus
Stored B Data to A Bus Stored B Data to A Bus
H
H
X
X
L
X Input
H
H H or L X
H
X Input
Output
Output
Real-Time A Data to B Bus Real-Time A Data to B Bus
Stored A Data to B Bus Stored A Data to B Bus
H
L H or L H or L H
H Output
Output
Stored A Data to B Bus
Stored B Data to A Bus
Stored A Data to B Bus
Stored B Data to A Bus
NOTES:
1. To prevent excess currents in the High-Z (isolation) modes, all I/O terminals should be terminated with 10kΩ to 1MΩ resistors.
2. The data output functions may be enabled or disabled by various signals at the OEAB or OEBA inputs. Data input functions are always
enabled, i.e., data at the bus pins will be stored on every low-to-high transition on the clock inputs.
3. Select control = L; clocks can occur simultaneously. Select control = H; clocks must be staggered in order to load both registers.
8-3