Subtracts the contents of the Y register from the memory only affecting flags

Operation

Y - M

Table

CPY | Compare Index Register Y to Memory
================================================

Y - M                            N V - B D I Z C
                                 + - - - - - + +

addressing       assembler    opc  bytes  cycles
------------------------------------------------
immediate        CPY #$nn      C0    2     2
absolute         CPY $nnnn     CC    3     4
zeropage         CPY $nn       C4    2     3

Flags

• Negative: 1 if bit 7 of result is 1; 0 otherwise
• Carry: 1 if X >= M; 0 otherwise
• Zero: 1 if X == M; 0 otherwise