Zeroko: Created page with "00 - LCD Base Address LCD Base Address == Synopsis == '''Port Number:''' 00h '''Function:''' LCD DMA Base Addre..."

2021-09-20T12:48:44Z

Created page with "00 - LCD Base Address LCD Base Address == Synopsis == '''Port Number:''' 00h '''Function:''' LCD DMA Base Addre..."

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[[Category:86:Ports:By_Address|00 - LCD Base Address]] [[Category:86:Ports:By_Name|LCD Base Address]]
== Synopsis ==
'''Port Number:''' 00h

'''Function:''' LCD DMA Base Address

This port controls the base address used as video memory by [[86:LCD_Controller#DMA|LCD DMA]].

=== Read Values ===
Because this port is write-only, its read behavior is the same as [[86:Memory_Mapping#Unused_Banks|Unused Banks]].

=== Write Values ===
* Bit 0-5: Bits 8-13 of LCD base address. The lower 8 bits of the address are always 0, & it is always in RAM page 0.
* Bit 6-7: Unused.

== Comments ==
* The OS sets this port to 7Ch, which results in video memory being accessible at FC00-FFFFh. However, it only sets it when the CPU is reset, so it should be set back to 7Ch (or 3Ch, BCh, or FCh, which behave identically) before returning to the OS.
* Changing this port causes the LCD image to change at the start (probably) of the next frame, so it can be used for double buffering, but not for a split screen effect.

86:Ports:00 - Revision history

Zeroko: Created page with "00 - LCD Base Address LCD Base Address == Synopsis == '''Port Number:''' 00h '''Function:''' LCD DMA Base Addre..."