Sharp MZ-3500 service manual Read/write from the Z-80 to V-RAM, Set GDC command code

MZ3500

4-12. Read/write from the Z-80 to V-RAM

Read/write of the Model 3500 V-RAM is done via the UPD7220GDC. There are two methods used to read/write data. The method (1) is used for the model 3500.

NO

YES

Set GDC command code

YES

Set parameter for the command

(1)Read/write via the 16 byte FIFO.

(2)Read/write of V-RAM in the DMA mode without intervention of the FIFO.

(Outline of the read/write data via the FIFO;

Method used to give a command to the GDC.

YES

Set parameter for the command.

I

Command must be given to the GDC in the same manner. On next page is the program of the above flowchart.

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