A programmable data link module is used on a time division multiplex data bus. The module is functional as an input device, an output device, or both as an input or output device. It can receive data from the data bus during a selected time slot for selected number of frames to control output devices connected to it. The data link module includes an input circuit for generating a data output signal data to the data bus in response to input signals from in input device coupled to the module. The input circuit includes a programmable input communication mode selector, allowing the data bus and the data link module to function with or without a host computer. The mode selector provides simplex or duplex.