| 摘要 |
PURPOSE:To uniform operation times of input/output devices which differ in execution priority by allowing a CPU to start all input/output devices under its control at a variable period and then enters the next startup cycle after confirming that all the input/output devices finish operating within one period. CONSTITUTION:The input/output devices IO1-IO6 which differ in execution priority P transmit and receive data to and from the CPU through a common bus CB. In this case, up to two IOs are permitted to occupy the bus CB and the IOs are given priority so that the IO1 has top priority and the priority decreases successively toward the IO6. The CPU checks operation states of all the IOs under its control at a constant period (t) and starts all the IOs in the next startup cycle after confirming that all the IOs report the completion of operation. The CPU confirms that <=1 IO uses the bus CB so that there is no IO which is left without using the bus CB within one startup cycle T, and transfers the right to use the bus CB to an IO enqueued for use. Then, the CPU enters the next start up cycle T' after receiving operation end reports from all the IOs. |
