JPS5790765A - Microprogram controller - Google Patents

Abstract

PURPOSE:To facilitate an diagnosis for an error detecting circuit, by providing an error occurrence byte designation bit that designates the byte that caused a fault to a microinstruction word plus an expected error code that can decides an error at the position of the designated byte. CONSTITUTION:The data of a register 200 is inverted and delivered through a parity bit inverting circuit 400 by an error designation occurrence indication signal produced based on the diagnosis designation of a microinstruction register 100 to be set to a register 500. The parity is checked by an error detecting circuit 600, and an error output is registered to a registering circuit 700. Then the output of the circuit 700 is compared 800 with the output of an error code register 900. Thus the normal operation of the circuit 600 is decided, and the microinstructions are successively read and execued. In this case, an expected error code 106 by which the designated byte position can be decided among the microinstruction words is directly fetched to the register 900. Then the AND condition is obtained between error occurrence byte designation bits 104/105 and a diagnosis designation bit 103 to obtain error designation occurrence indication signals 111 and 121.