Changes

V9990

479 bytes added, 14:04, 1 January 2019
/* Command Engine */
== Command Engine ==
 
=== 'Stand-by mode' ===
 
* "Stand-by mode" where both bits of DSPM are 1 appear to be identical in operation to the bitmap mode when display is enabled.
=== Coordinates ===
=== Commands ===
 
* Registers specific to each command can be initialized in any order. "op" register (R52) should be written last so that it uses the correct register settings.
* Always setup DY before commands that use it. There is a bug where pixels may not be committed to the expected vram location. Seen with lmmv instruction.
==== BMLL ====
* If source and destination ranges overlap then there can be some unexpected data written. You should avoid overlapped areas or keep them at least 2 bytes apart.
* When DIX=0, then both source and destination vram addresses are incremented. When DIX=1, then both source and destination vram addresses are decremented.
* I can't currently see what DIY does in respect of BMLL. It seems it has no effect.
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