| 摘要 |
<p>PURPOSE: To display a character screen without generating delay by directly writing character information from a main CPU to a character memory at the time of displaying the character information. CONSTITUTION: In order to write a character code and attribute data in the character memory 9, the main CPU 1 outputs an address of the memory 9 to a system bus 3. An address decoding circuit 20 detects the address and outputs a bus use request permission signal to be a request for using a local bus to a sub-CPU 5 through a line 25. The sub-CPU 5 outputs a bus switching signal for connecting the memory 9 to the bus 14 to a bus switching circuit 40 through a line 27. Thereby the main CPU 1 can directly access the memory 9. Consequently processing for a character display request is accelerated.</p> |
