HD74HC646 Datasheet, PDF (2/10 Pages) Hitachi Semiconductor – Octal Bus Transceivers/Registers with Multiplexed 3-state outputs

HD74HC646/HD74HC648
Function Table
Inputs
Control
Clock Select Data I/O Data I/O Operation or Function
G
Direction BA AB AB BA A1 thru A8 B1 thru B8 HD74HC646
HD74HC648
H
X
X X X X Z (Input) Z (Input) Isolation
Isolation
H
X
H H Z (Input) Z (Input) Store A & B data Store A & B data
L
L
X X X L Output
Z (Input) B real-time data to B real-time data to
A bus
A bus
L
L
H H X H Output
Z (Input) B stored data to A B stored data to A
bus
bus
L
L
L L X H Output
Z (Input) B stored data to A B stored data to A
bus
bus
L
H
X X L X Z (Input) Output
A real-time data to A real-time data to
B bus
B bus
L
H
H H H X Z (Input) Output
A stored data to B A stored data to B
bus
bus
L
H
L L H X Z (Input) Output
A stored data to B A stored data to B
bus
bus
Real-time transfer
Bus B to Bus A
Real-time transfer
Bus A to Bus B
2