74HCT640

The 74HCT640 is high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.

The 74HCT640 is octal transceivers featuring inverting 3-state bus compatible outputs in both send and receive directions.

The "640" features an output enable (OE) input for easy cascading and a send/receive (DIR) for direction control.
OE controls the outputs so that the buses are effectively isolated. The "640" is similar to the "245" but has inverting outputs.