| 摘要 |
PURPOSE:To attain the change and addition of a character pattern and to simplify the constitution of a character pattern controller, by deciding whether the character pattern corresponding to a character code exists in the 1st or 2nd memory and obtaining the address of the character pattern when the pattern exists in the 2nd memory. CONSTITUTION:A circuit 2 is connected to a host device and also to a screen memory 1 storing character patterns, and the output of the memory 1 is supplied to a character code register 3. The output of the register 3 is supplied to a mask ROM4, a map ROM5 and a code discriminator 6. Furthermore, a timing control part 10 is connected to the memory 1, the register 3, a shift register 8 and a raster counter 11 respectively. The outut of the counter 11 is connected to the ROM4 and the address input of a PROM7. Then the discriminator 6 refers to the ROM switching bit to decide whether the ROM4 or the PROM7 is set under an enable-state. When a character pattern exists in the PROM7, the corresponding address is obtained. Thus the change and addition are facilitated for the character pattern.
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