| 摘要 |
PURPOSE:To observe the state of a bus by providing a latch circuit on a signal line at the READ side of a bus control part, adding a specific address to the latch circuit and performing the latch writing and reading actions. CONSTITUTION:In a bus diagnosis mode are written to the specific address X of a data latch 221. Then data are delivered onto a bus through a transmission buffer 21 and also written to the latch 221. Then the contents of the latch 221 are read through a reception buffer 22 after the address X is read. Therefore the written data is different from the read data if a line is fixed to Vcc or GND on the data lines (BD0-BD7) on the bus. Thus a defective area can be decided. |
