Microcomputer with table-read and table-write instructions

摘要

A system for real-time digital signal processing employs a single-chip microcomputer device having separate on-chip program ROM and data RAM, with separate address and data paths for program and data; however, the accumulator in the data path may be used as a program address source for table-read and table-write, for example. An external program address bus allows off-chip program fetch in an expansion mode, with the opcode returned by an external data bus. A bus interchange module allows transfer between the separate internal program and data busses in special circumstances, such as accumulator addressing. The internal busses are 16-bit, while the ALU and accumulator are 32-bit. A multiplier circuit produces a single state 16x16 multiply function separate from the ALU, with 32-bit output to the ALU. One input to the ALU passes through a 0-to-15 bit shifter with sign extension.