| 摘要 |
<p>PURPOSE:To ensure the power supply and to attain the use of a common I/O device so log as any terminal requires the use by leaving a timer value of reservation request from each terminal equipment and a maximum value of a timer value for initial setting. CONSTITUTION:A terminal equipment uses DA as a shared I/O device address, SA as its own address C as request kind, sets them to the item FF and sends the reservation request to the shared I/O device while using the D as the reservation timer by the shared I/O device. The shared I/O device receives an instruction of CPU when the reception frame has a relation of C=FF (hexadecimal number), a control section 32 opens a read gate 44 and sends the value of a subtractor 36 to the CPU. The read value is compared with the value D in a frame and when the D is smaller, since the setting time is longer, the request from the terminal equipment is disregarded. When the D is larger, the control section 32 gives a load signal 37 by the instruction of the CPU, the value D passes through the gate 40 and reset in the subtractor 36. Thus, any terminal equipment stops using, the power supply of the shared I/O device is shut off. The power supply OFF management of the shared I/O is attained by having only to send the request set with the time desired by itself.</p> |
