The IN74HC651A is identical in pinout to the LS/ALS651. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALSTTL outputs.
These devices consist of bus transceiver circuits, D-type flip-flop, and control circuitry arranged for multiplex transmission of data directly from the data bus or from the internal storage registers.

The IN74HC651A has inverted outputs.
• Outputs Directly Interface to CMOS, NMOS, and TTL
• Operating Voltage Range: 2.0 to 6.0 V
• Low Input Current: 1.0 μA
• High Noise Immunity Characteristic of CMOS Devices