Routines
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57405: Compare Slot With Site
Used by the routine at MakeTiles.
Compares a slot for a pick-up with a site, using the column, the row and the position. The result is that the zero flag is set if the slot holds the pick-up for the site, and is clear if not or if the slot is free.
Input
IX Address of the site
IY Address of the slot
Output
F Zero flag set if the slot has the pick-up
CompareSlotWithSite 57405 LD A,(IY+0) Read offset 0 of IY.
57408 INC A Advance A.
57409 JR Z,CompareSlotWithSite_Free Jump to CompareSlotWithSite_Free if the zero flag is set.
57411 LD A,(IX+0) Read offset 0 of IX.
57414 CP (IY+1) Return if A is not the byte at offset 1 of IY.
57417 RET NZ
57418 LD A,(IX+1) Read offset 1 of IX.
57421 CP (IY+4) Return if A is not the byte at offset 4 of IY.
57424 RET NZ
57425 LD A,(IX+2) Read offset 2 of IX.
57428 CP (IY+2) Return if A is not the byte at offset 2 of IY.
57431 RET NZ
57432 LD A,(IX+3) Read offset 3 of IX.
57435 CP (IY+5) Compare A with the byte at offset 5 of IY.
57438 RET Return.
CompareSlotWithSite_Free 57439 OR %00000001 Set the bits of A that are set in 1.
57441 RET Return.
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