The ´BCT640 bus transceiver is designed for asynchronous communication between data buses. These devices transmit data from the A bus to the B bus or from the B bus to the A bus depending upon the level at the direction-control (DIR) input. The output-enable () input can be used to disable the device so that the buses are effectively isolated. The SN54BCT640 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74BCT640 is characterized for operation from 0°C to 70°C.