Abstract: A PCM encoder which receives asynchronous serial data and incorporating the serial data and eight channels of analog data into a PCM data stream. The encoder includes a microprocessor which processes the serial data provided in eight bit digital words and the analog data which the microprocessor converts to twelve bit digital words. The encoder also has a programmable gate array which receives six bits of data during each transfer of data from the microprocessor to the gate array. The gate array for the PCM encoder also receives a Frame Sync, and then processes the data to provide a data stream containing NRZL data and Bi Phase data.