A digital signal processor (DSP) employs a variable-length instruction set. A portion of the variable-length instructions may be stored in adjacent locations within memory space with the beginning and ending of instructions occurring across memory word boundaries. The instructions may contain variable numbers of instruction fragments. Each instruction fragment causes a particular operation, or operations, to be performed allowing multiple operations during each clock cycle. The DSP includes multiple data buses, and in particular three data buses. The DSP may also use a register bank that has registers accessible by at least two processing units, allowing multiple operations to be performed on a particular set of data by the multiple processing units, without reading and writing the data to and from a memory. an instruction fetch unit that receives instructions of variable length stored in an instruction memory. An instruction memory may advantageously be separate from the three data memories. An instruction decoder decodes the instructions from the instruction memory and generates control signals that cause data to be exchanged between the various registers, data memories, and functional units, allowing multiple operations to be performed during each clock cycle.