| 摘要 |
PURPOSE:To prevent the flickering produced on a display screen despite the writing and display requests given asynchronously, by providing an access arbitrating circuit to keep an access request given from a CPU during a display period waiting to a display memory. CONSTITUTION:A synchronism control signal 12 for access request given from a display timing generating circuit 3 is set at an H level together with an access given to a display RAM 2 via the circuit 3, and a multiplexer 6 and a display device 21 is working. Under such conditions, an access request signal 8 given from a CPU 1 becomes active. Thus, the access request given from the CPU 1 is kept waiting by an access arbitrating circuit 10. Then, the request kept waiting is validated by the circuit 10 when the display period of the circuit 3 is over. Then, an access is given to the RAM 2 from the CPU 1 for execution of a rewriting job. Thus, the flickering occurring on a display screen can be avoided with no conflict produced between writing and display requests if given asynchronously with each other.
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