Sharp MZ-5500 - Page 100

V MA= VAD-WDA
°WDC programming
Write to the WDC and the mapping RAM is limited only to the vertical
flyback time. Whereas, one window must be programmed at a time in a single
vertical flyback time to set four windows. Special attention must be paid
to the program timing for the mapping RAM.
Set SAD to GDC
~Ä, VDS, and.priority values
should be provided before the
VSYNC check and they should
be set in succession at VSYNC.
Set P:iOrity 1\
As VSYNC is with IRQ of the
master (8259A), this
interrupt may be used.
END
Priority, VHA, and ' VDS may not be programmed one ' at a time necessarily;
they . may be set altogether ., if possible. However, the mapping RM~ shCluld
preferably be programmed for a window one at a time during the vertical
flyback time in order to prevent distortion in the display.
°Use of the WDC
°Window overlay , must be done by changing the priority.
°Relocation of the window must be done by changing the mapping RAH along
with VMA.
Set VMA, VDS
rI
mapping RAH
q'!
cl