The 'ABT16657 contain two noninverting octal transceiver sections with separate parity generator/checker circuits and control signals. For either section, the transmit/receive (1T/R\ or 2T/R\) input determines the direction of data flow. When 1T/R\ (or 2T/R\) is high, data flows from the 1A (or 2A) port to the 1B (or 2B) port (transmit mode); when 1T/R\ (or 2T/R\) is low, data flows from the 1B (or 2B) port to the 1A (or 2A) port (receive mode). When the output-enable (1 or 2) input is high, both the 1A (or 2A) and 1B (or 2B) ports are in the high-impedance state.

Odd or even parity is selected by a logic high or low level, respectively, on the 1ODD (or 2ODD) input. 1PARITY (or 2PARITY) carries the parity bit value; it is an output from the parity generator/checker in the transmit mode and an input to the parity generator/checker in the receive mode.