Vince Weaver 98b3bc9902 pt3: have player calculate total time
it takes a while
2019-05-14 14:25:13 -04:00
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PT3_player



ASR = CMP #$80 / ROR



Notes:

signed 8-bit comparison
see http://6502.org/tutorials/compare_beyond.html#2.2

          SEC       ; prepare carry for SBC
          SBC NUM   ; A-NUM
          BVC LABEL ; if V is 0, N eor V = N, otherwise N eor V = N eor 1
          EOR #$80  ; A = A eor $80, and N = N eor 1
    LABEL

If the N flag is 1, then A (signed) < NUM (signed) and BMI will branch
If the N flag is 0, then A (signed) >= NUM (signed) and BPL will branch