| 摘要 |
PURPOSE:To prevent plural processors in a multiprocessor constitution from accessing the same device at the same time, by deciding on states of input/output control signals of plural microprocessors by comparison, and selecting a microprocessor whose input/output control signal is to be passed. CONSTITUTION:When a microprocessor A connected to a terminal 1-1 through an input/output control signal line and a microprocessor B connected to a terminal 1-2 through an input/output control signal line are to access a device selection signal line S10 at the same time, the signal lines S6 and S7 are both held at a level 1 at the same time. A signal line S16 has a level 0 and a signal line S18 has the level 1 through the inversion of an inverting circuit 15. An NAND circuit 17 holds a signal line S20 at the level 0 and holds a signal line S11 at the level 1 forcibly. A signal line S12 holds the level 0 to stop a CPU temporarily. At the same time, a selecting circuit 10 selects a signal line S15 to allow output to a signal line S9. |
