Routines
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41411: Move Up A Row
Used by the routines at FadeOutPlayfield, ClearPlayfield, PrintCharacter, PrintWideCharacter, BuildCarriedItemGraphic, DrawRows, EraseRows, DrawBitmap, DrawFrame, DrawFuelGaugeFrame, DrawEdgePixels, MoveUpEdgeRows, FillEdgeRowPair, BeginLife and FillStripWithPattern.
Moves a screen address up one pixel row.
Input
HL Screen address
Output
HL Screen address of the row above
MoveUpARow 41411 DEC H Move up a pixel row.
41412 LD A,H Fetch the high byte of the address.
41413 INC A Add one.
41414 AND %00000111 Keep the bits that give the pixel row.
41416 RET NZ Return if the row is still in the same cell.
41417 LD A,L Fetch the low byte of the address.
41418 SUB 32 Move up a row of cells.
41420 LD L,A Store it.
41421 RET C Return if that crossed a third of the screen.
41422 LD A,H Fetch the high byte of the address.
41423 ADD A,8 Add eight to correct it.
41425 LD H,A Store it.
41426 RET Return.
View the equivalent code in;
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