| 摘要 |
PURPOSE:To prvent software from being copied and then to make a test by reading a program of a microcomputer by applying a test pulse to a test-function common terminal. CONSTITUTION:The contents of program counter (PC)4 are cleared and the contents of address 0 of internal ROM3 are transferred to instruction register (IR)5. With a pulse applied to test-function common terminal 9, AND circuit 8 opens to reset IR5 and the contents of ROM3 are written in output port 2 and then output. Through the same operation repeated as mentioned above, AND circuit 7 detects the contents of PC4 reaching address N to set flip-flop 6 and AND circuit 8 is closed to inhibit a test pulse. Therefore, PC4 indicates address M with the instruction of address N, i.e. a jump instruction to address M. |
