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CMP: Difference between revisions

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'''CMP''' (Compare) is a 65x instruction that compares the value of the [[accumulator]] to something.  Internally, this is done via a subtraction, but the difference is not stored anywhere.  CMP only does unsigned comparisons.  In [[immediate addressing]] only, CMP is a total of 3 bytes long when the accumulator is 16 bits wide.  Unlike [[SBC]], the [[carry flag]] does not affect CMP.
'''CMP''' (Compare) is a 65x instruction that compares the value of the [[accumulator]] to something.  Internally, this is done via a subtraction, but the difference is not stored anywhere.  CMP only does unsigned comparisons.  In [[immediate addressing]] only, CMP is a total of 3 bytes long when the accumulator is 16 bits wide.  Unlike [[SBC]], the [[carry flag]] does not affect CMP.
If the subtraction required a borrow, the carry flag is cleared (otherwise it is set).


===== Cycle Penalties =====
===== Cycle Penalties =====

Revision as of 21:42, 27 June 2024

Basic Info
Addressing Mode Opcode Length Speed
Immediate C9 2 bytes* 2 cycles*
Absolute CD 3 bytes 4 cycles*
Absolute Long CF 4 bytes 5 cycles*
Direct Page C5 2 bytes 3 cycles*
Direct Page Indirect D2 2 bytes 5 cycles*
Direct Page Indirect Long C7 2 bytes 6 cycles*
Absolute Indexed by X DD 3 bytes 4 cycles*
Absolute Long Indexed by X DF 4 bytes 5 cycles*
Absolute Indexed by Y D9 3 bytes 4 cycles*
Direct Page Indexed by X D5 2 bytes 4 cycles*
Direct Page Indexed Indirect by X C1 2 bytes 6 cycles*
Direct Page Indirect Indexed by Y D1 2 bytes 5 cycles*
Direct Page Indirect Long Indexed by Y D7 2 bytes 6 cycles*
Stack Relative C3 2 bytes 4 cycles*
Stack Relative Indirect Indexed by Y D3 2 bytes 7 cycles*
Flags Affected
N V M X D I Z C
. . . . .

CMP (Compare) is a 65x instruction that compares the value of the accumulator to something. Internally, this is done via a subtraction, but the difference is not stored anywhere. CMP only does unsigned comparisons. In immediate addressing only, CMP is a total of 3 bytes long when the accumulator is 16 bits wide. Unlike SBC, the carry flag does not affect CMP.

If the subtraction required a borrow, the carry flag is cleared (otherwise it is set).

Cycle Penalties

See Also

External Links

Retrieved from "https://sneslab.net/mw/index.php?title=CMP&oldid=15882"