| 摘要 |
PROBLEM TO BE SOLVED: To carry out a test with a simple circuit without the need of supplying a test address from outside by storing a ROM test starting address in CPU, converting the read data to a nop (no operation) command and supplying it to CPU. SOLUTION: In testing CPU 13 and a ROM 11 incorporated in one chip, a control signal ROMTEST for the test is set for 'H'. An interrupt controller 35 transmits an interrupt factorial signal to CPU 13. With a ROM test starting address set preliminarily in the address space of CPU 13, it is loaded in a program counter. An address decoder 17b accesses an address specified by the program counter. ROM 11 outputs the data of the specified address to a data bus 23. A data bus control circuit 37 converts all data outputted to the data bus 23 into a nop command and transmits it to CPU 13. Thus, the program counter is counted up, with ROM accessed successively. |
