This part is a kind of semiconductor called 74643.

Function of this product has True-Inverting Octal TRI-STATE Transceiver.

Manufacturers : National Semiconductor

Image and pinout :

Some of the text within the PDF file :

MM54HCT640 MM74HCT640 Inverting Octal TRI-STATE Transceiver MM54HCT643 MM74HCT643 True-Inverting Octal TRI-STATE Transceiver February 1988 MM54HCT640 MM74HCT640 Inverting Octal TRI-STATE Transceiver MM54HCT643 MM74HCT643 True-Inverting Octal TRI-STATE Transceiver General Description These TRI-STATE bi-directional transceivers utilize advanced silicon-gate CMOS technology and are intended for two-way asynchronous communication between data buses They have high drive current outputs which enable high speed operation even when driving large bus capacitances These circuits possess the low power consumption of CMOS circuitry yet have speeds comparable to low power Schottky TTL circuits All devices are TTL input compatible and can drive up to 15 LS-TTL loads and all inputs are protected from [ ... ]

74643 PDF Datasheet Download