The IN74AC651 is identical in pinout to the LS/ALS651, HC/HCT651. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALS outputs.
These devices consists 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 IN74AC651 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, 0.1 µA @ 25°C
• High Noise Immunity Characteristic of CMOS Devices
• Outputs Source/Sink 24 mA