| 摘要 |
<p>A microcomputer which may be implemented by MOS/LSI techniques on a single semiconductor chip includes a data processing system having control logic means 26, means for exchanging data with at least one peripheral device PE through at least one data transfer port 12-18, an ALU 24, and program storage means 22 in which a set of microprograms is stored including at least a first microprogram for controlling the execution of instructions. The ALU 24 has two inputs fed from respective outputs of an 8-bit accumulator 30 and a scratch pad store 40, the latter comprising 64 8-bit registers, and an output 54 fed back to inputs of the accumulator and scratch pad store. The scratch pad store 40 has a 6-bit address input 60 which can be fed with (a) a 6-bit address from an indirect address register 58, (b) four bits from an instruction register 42 and two zero bits, or (c) four bits direct from the control logic means 26 to directly access the lowest 16 scratch pad registers in response to certain instructions. Interrupt processing is also described. <IMAGE></p> |
