System and method for protocol conversion in a communications system

Abstract

The present invention entails a programmable data communications protocol conversion unit (PCU) and method. The PCU is a processor circuit which includes a means for performing full parallel, partial parallel, and bit data transfers. In particular, a bit assembly register is employed to assemble partial parallel data blocks which comprise data with a number of bits that is less than the order of the data bus of the PCU. The bit assembly register further includes the capability of writing the partial parallel data block to predetermined locations using a full parallel transfer and a shadow bus with bits indicating the validity of the particular bits in the data block transferred. The particular circuits receiving partial parallel writes include a register for receiving data and a register for receiving the corresponding shadow bits. Invalid data written to these registers is ignored while valid data is shifted accordingly, for example, out to a serial interface. The PCU further includes a task specific circuit for performing bit alignment and other tasks and a task specific circuit for generating cyclic redundancy check (CRC) data. The later circuit can create CRC data for any number of protocols as the circuit is highly configurable with a bit shift register of varying lengths.