ROM CHECKING SYSTEM

PURPOSE:To execute completely an ROM check through a few external output terminal by outputting serially the output of a latched ROM in accordance with a switching signal, and checking by one bit each of contents of the ROM. CONSTITUTION:A data of (n)-bit, etc. from the ROM6 is impressed and latched to an input terminal R of (n) flip-flops FF1-FFn for forming a latching circuit 7. The output of the flip-flop of a lower stage except the flip-flop FF1 is impressed to the input terminal I of these flip-flops. Subsequently, the flip-flop is brought to a multistage operation in accordance with a switching signal Te to output a latch output serially and successively from the flip-flops FF1, FF2-, and compared with an instruction data stored in an RAM, etc. through a common external output terminal to check the ROM. According to this constitution, the ROM check can be executed completely through a few external output terminal.