Data unpacker

A data unpacker receives packed parallel input data words having a fixed width of m bits, and it outputs parallel data words having a variable width of n bits. An input register (12-14) stores the received words and applies them to a bit shifter (20). The bit shifter shifts the received data by a number of bit positions indicated by a shift control signal, and the shifted data is output therefrom as a parallel output word having n valid bits. The number n for each output word is received by the unpacker as a binary number. When n>/=m, a most significant (MSB) bit portion of that number is applied as first MSB control signal. The least significant bit (LSB) portion of n is applied to an adder (30) which adds subsequently received LSB portions to provide a running sum. When the running sum is equal to or greater than m, the adder provides a second MSB control signal, corresponding to the most significant bit of the running sum. The least significant bit portion of the running sum is applied to th ebit shifter as the shift control signal. A logic circuit receives the first and second control MSB control signal and it provides in response to either of these signals a READY FOR DATA control signal indicating the input register is ready to receive the next input word, and a DATA VALID OUT control signal indicating the the bit shifter is ready to output the parallel output word.