| 摘要 |
<p>PURPOSE:To check programs surely, by providing a circuit, which makes instructions JMP and CALL ineffective, in the output side of an instruction decoder in the one-chip microcomputer having a user read-only memory. CONSTITUTION:Circuit means MOS transistors Q2 and Q1 which make instructions CALL and JMP in a program ineffective are provided on the output line of an instruction decoder 10 which decodes instructions read out from a program read-only memory 1. Thus, when contents of the program are checked in the user side, instructions JMP and CALL are made ineffective and are regarded as no operations, and an address counter of the memory 1 is counted up by +1, and the program of the memory 1 is forcedly run from address 0 to the last address independently of instructions JMP and CALL. Consequently, the program written in the memory 1 is executed completely, and the user program is checked surely.</p> |
