Rapid prototyping with programmable control paths

The provision of a programmable control path allows a designer to experimentally build and evaluate many different instruction sets and data paths in a short period of time. For this approach to be practical, the designer needs a way to quickly modify the control path hardware to reflect the changes in the instruction set. To this end, we describe a flexible and efficient method for generating control logic information, given an instruction set. All the information regarding the instruction set, namely, the mnemonics, the opcodes and the values of the control lines for the data path, are stored in a single file. This information is used by the assembler to assemble programs as well as generate control path programming information, which in turn is used to set up the new control path. We also show a way of searching the design space to iteratively modify an instruction set to satisfy the hardware constraints. Using this method we have successfully built a prototype of the Micro Grain Array processor. In fact we were able to submit the board for fabrication before finalizing an instruction set.<
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