LD BC,&FF64
LD A,14
OUT (C),CA
LD BC,&FF63
LD A,0
LD BC,&FF64
LD A,14
OUT (C),CA
LD BC,&FF63
LD A,3
LD BC,&FF64
LD A,14
OUT (C),CA
LD BC,&FF63
LD A,3
LD BC,&FF64
LD A,14
OUT (C),CA
LD BC,&FF63
LD A,2
So you need to know when each mask register is used and you need to understand the logical->physical VRAM mapping.
===== Write Mask in P1 mode =====
* Document states "In P1 mode, writing is prohibited on the side not specified as the transfer destination. (Layer "A":R#46, Layer "B":R#47)". I haven't discovered what this actually means yet.
===== Write Mask in bitmap and standby modes =====
* 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.
* CE will be set to 1 in status when operation has started. CE will be set to 0 in status when operation has completed. CE will be set to 1 in interrupt when operation has completed.
==== Command Recommendations ====
* Pixels are written according to physical vram. Foreground low byte is for physical VRAM0. Background low bytes is for physical VRAM 1. Foreground high byte is for physical VRAM1, and background high byte is for physical VRAM 1.
* To draw a font in the same colour ensure the same colour is repeated for all pixels in FC and BC (i.e. for 8 bit mode set FC upper and lower byte to the same, and set BC upper and lower byte to the same.)
* For LOP, SC comes from background colour or foreground colour depending on the value of the bit.
==== SRCH ====
* To know if a match has been found always look at the status bit. BD will be 1 for a match and 0 for no match. The border x coordinate is always set to something even if there is no match.
* When searching sx and sy are masked before use. If the width is 256, then sx is masked with 255 before use.
[[Category:HardwareElectronic Component]]