The KK74ACT643 is identical in pinout to the LS/ALS643, HC/HCT643. The KK74ACT623 may be used as a level converter for interfacing TTL or NMOS outputs to High Speed CMOS inputs. The KK74ACT643 is a 3-state transceiver that is used for 2-way asynchronous communication between data buses. The device has an active-low Output Enable pin, which is used to place the I/O ports into high-impedance states. The Direction control determines whether data flows from A to B or from B to A. TTL/NMOS Compatible Input Levels Outputs Directly Interface to CMOS, NMOS, and TTL Operating Voltage Range: 4.5 to 5.5 V Low Input Current: 1.0 A; 0.1 A @ 25C Outputs Source/Sink 24 mA