COMPRESSING CONTROL ROM FOR VLSI MICROPROGRAMMED MICROPROCESSORS.

By taking advantage of information redundancy and MOS structures, control ROMs for microprogrammed microprocessors can be considerably reduced. The Compressed Control ROM (CCROM) method for reducing control ROMs is described in terms of a simple example that compares the fully horizontal (unencoded) approach, the normal partially encoded approach, and the CCROM approach. Due to using CCROM, the effective cost of control ROM is considerably reduced, and this in turn can have a significant effect on the design approach by making it more cost effective to implement control signals directly from the control ROM rather than from random logic decodes.