MM54HCT640 MM74HCT640 Inverting Octal TRI-STATE Tr.
National Semiconductor
74643 - True-Inverting Octal TRI-STATE Transceiver
MM54HCT640 MM74HCT640 Inverting Octal TRI-STATE Transceiver MM54HCT643 MM74HCT643 True-Inverting Octal TRI-STATE Transceiver February 1988 MM54HCT64.