| 摘要 |
PURPOSE:To enable a CPU to carry on internal processing by attaching or detaching an optional I/O board to or from a CPU board during operation. CONSTITUTION:A signal holding circuit 13 can not receive the ground voltage of a connection signal generation part 22, and receives a high-level connection signal 1i and outputs a high-level connection holding signal 1b to a selector circuit 14 when the I/O board 20 is detached from the CPU board 10. The selector circuit 14 receives the high-level connection holding signal 1b and does not send out an operation inhibition signal 1c so as to permit a 1st timer circuit 15 to operate, and the 1st timer circuit 15 is allowed to operate and starts measuring the time once detecting an I/O request signal 1a for the I/O board 20 from the CPU 11 thereafter to outputs a time-limit passing signal 1d a specific time later to the operation permit signal input terminal and interruption input terminal of the CPU 1, so that the CPU 1 restarts the internal processing. |
