PROGRAMMABLE ACCELERATOR FOR A PROGRAMMABLE PROCESSOR SYSTEM

A programmable multi-mode accelerator is disclosed for use with a programmable processor or microprocessor. The programmable multi-mode accelerator allows a programmable processor to execute specific algorithms, such as certain types of finite impulse response (FIR), correlation and Viterbi computations, that require low-precision operations at an extremely high rate. The accelerator extends the digital signal processor's performance into the required range for low-precision computations. The accelerator can be coupled with the main data path of a programmable processor or microprocessor and can directly read and write to the main register files of the programmable processor. In an illustrative implementation, the accelerator data path accesses its input values (source operands) directly from a main register file of the programmable processor and writes results back into a second main register file. The accelerator allows a plurality of low-precision algorithms requiring primarily addition or multiply-add computations, such as finite impulse response, correlation and Viterbi computations, to utilize the same adder cells. The accelerator includes a multi-mode adder that can be programmatically reconfigured to perform various addition computations. In a first mode, referred to as the “single-add mode,” the adder operates as a 17-input 16-bit adder. The single-add mode can be utilized to perform finite impulse response and correlation computations. The second mode, referred to as the “ACS mode,” can be utilized to perform Viterbi computations. The accelerator has a small instruction set and instruction memory and, once started by the main data path, the accelerator executes its own instruction stream. In addition, the accelerator includes a delay line having delays of z−1 or z−2.