PURPOSE: To omit addition of a new instruction for accesses despite the increase of the number of special registers by attaining an access to a desired special register just with change of the register number and without changing the operation code.
CONSTITUTION: An LSI chip 1 forming a microprocessor contains a micro-ROM storing a microprogram. The ROM 2 receives an access from a microaddress decoder 5 and the microinstructions forming the microprogram are successively read out. The address which is produced by a microaddress generating circuit 4 based on an operation code of a microinstruction fetched by an instruction register 3 is supplied to the decoder 5. Thus the decoder 5 decodes said address to read out the first instruction of a series of microinstruction groups that execute the corresponding macroinstruction. Then the control signal is produced to an execution unit 6, etc.
OOTA YUJI
KIDA HIROYUKI
| JPS5757345A | 1982-04-06 |