The SN74FB2040 device is an 8-bit transceiver designed to translate signals between TTL and backplane transceiver logic (BTL) environments. The B port operates at BTL-signal levels. The open-collector B ports are specified to sink 100 mA. Two output enables (OEB and OEB) are provided for the B outputs. When OEB is high and OEB is low, the B port is active and reflects the inverse of the data present at the A-input pins. When OEB is low, OEB is high, or VCC is less than 2.1 V, the B port is turned off. The A port operates at TTL-signal levels and has separate input and output pins. The A outputs reflect the inverse of the data at the B port when the A-port output enable (OEA) is high. When OEA is low or when VCC is less than 2.1 V, the A outputs are in the high-impedance state. Pins are allocated for the four-wire IEEE Std 1149.1 (JTAG) test bus. TMS and TCK are not connected and TDI is shorted to TDO.