Routines
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A1C3: 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 A1C3 DEC H Move up a pixel row.
A1C4 LD A,H Fetch the high byte of the address.
A1C5 INC A Add one.
A1C6 AND %00000111 Keep the bits that give the pixel row.
A1C8 RET NZ Return if the row is still in the same cell.
A1C9 LD A,L Fetch the low byte of the address.
A1CA SUB $20 Move up a row of cells.
A1CC LD L,A Store it.
A1CD RET C Return if that crossed a third of the screen.
A1CE LD A,H Fetch the high byte of the address.
A1CF ADD A,$08 Add eight to correct it.
A1D1 LD H,A Store it.
A1D2 RET Return.
View the equivalent code in;
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