| Load routines

32768: Collect one bit from tape

Used by the routine at 32815.
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.
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