Routines
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41395: Move Up A Row In DE
Used by the routines at AddToStack and DrawFrame.
Moves a screen address up one pixel row.
Input
DE Screen address
Output
DE Screen address of the row above
MoveUpARowDE 41395 DEC D Move up a pixel row.
41396 LD A,D Fetch the high byte of the address.
41397 INC A Add one.
41398 AND %00000111 Keep the bits that give the pixel row.
41400 RET NZ Return if the row is still in the same cell.
41401 LD A,E Fetch the low byte of the address.
41402 SUB 32 Move up a row of cells.
41404 LD E,A Store it.
41405 RET C Return if that crossed a third of the screen.
41406 LD A,D Fetch the high byte of the address.
41407 ADD A,8 Add eight to correct it.
41409 LD D,A Store it.
41410 RET Return.
View the equivalent code in;
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