PROGRAMMABLE ARRAY FOR ON-CHIP CONTROL STORE FOR CORRECTING MICROCODE

摘要

PURPOSE: To obtain a device for correcting a microcode having an error included in a microprogrammed processor control store. CONSTITUTION: This device includes a detecting circuit 900 which detects the instruction code corresponding to the micro instruction having the error in the main control store ROM 400 of a system and a programmable array used as a memory region for a substitutive micro instruction. This detecting circuit 900 is a circuit operating as a logic NOR circuit and is used for detecting the instruction code effective for the micro instruction corresponding to the microcode sequence including the error. The programmable array consists of two loadable RAMs 410, 420 including a microcodes having no errors substituting for a microcode having error. The detection and correction are induced in parallel with decoding of the instruction so as not to affect the cycle time of the system.