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Load routines |
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Used by the routine at 32815.
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32768 | INC SP | Place the address 0 on the stack above the current return address, so the Spectrum will reset if there's a loading error | |||||
32769 | INC SP | ||||||
32770 | EX (SP),HL | ||||||
32771 | LD H,0 | ||||||
32773 | LD L,H | ||||||
32774 | EX (SP),HL | ||||||
32775 | DEC SP | ||||||
32776 | DEC SP | ||||||
32777 | LD A,6 | ||||||
32779 | CALL 32785 | Listen for one edge | |||||
32782 | RET NC | Return if no edge was found within the time limit | |||||
This entry point is also used by the routine at 32815.
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32783 | LD A,11 | Wait a bit | |||||
32785 | DEC A | ||||||
32786 | JR NZ,32785 | ||||||
32788 | AND A | Reset the carry flag | |||||
32789 | INC B | Have we run out of time to find an edge? | |||||
32790 | RET Z | Return with the carry flag reset if so | |||||
32791 | LD A,127 | Collect an EAR port reading in bit 6 of A | |||||
32793 | IN A,(254) | ||||||
32795 | RRA | Move it to bit 5 of A | |||||
32796 | AND A | In the analogous ROM routine, the instruction here is 'RET NC', causing a return if BREAK was pressed; in this routine, that behaviour is disabled (pressing BREAK does nothing) | |||||
32797 | XOR C | Compare this EAR port reading with the previous one | |||||
32798 | AND 32 | ||||||
32800 | JR Z,32789 | Jump back if they are the same (i.e. no edge was found) | |||||
32802 | LD A,C | Alternate the border colour | |||||
32803 | CPL | ||||||
32804 | LD C,A | ||||||
32805 | AND 7 | ||||||
32807 | OR 8 | ||||||
32809 | OUT (254),A | ||||||
32811 | SCF | Signal: an edge was found within the time limit | |||||
32812 | RET | Return with B indicating the time taken to find the edge |
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