We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS

CPX: Difference between revisions

From SnesLab
Jump to: navigation, search
(to something)
(subtrahend)
Line 45: Line 45:
|}
|}


'''CPX''' (Compare X) is a 65x instruction that compares the value of the [[X index register]] to something.  Internally, this is done via a subtraction, but the difference is not stored anywhere.  Thus, the purpose of CPX is to setup the flags.  The index register X is the minuend.  The contents at the effective address (when not using immediate data) and the X index register both remain unchanged.
'''CPX''' (Compare X) is a 65x instruction that compares the value of the [[X index register]] to something.  Internally, this is done via a subtraction, but the difference is not stored anywhere.  Thus, the purpose of CPX is to setup the flags.  The index register X is the minuend.  Depending on the addressing mode used, the subtrahend will be either an immediate value or the value stored at the effective address specified by the operand.  The contents at the effective address (when not using immediate data) and the X index register both remain unchanged.


CPX assumes its operands are unsigned.
CPX assumes its operands are unsigned.

Revision as of 06:54, 22 July 2024

Basic Info
Addressing Mode Opcode Length Speed
Immediate E0 2/3 bytes 2 cycles*
Absolute EC 3 bytes 4 cycles*
Direct Page E4 2 bytes 3 cycles*
Flags Affected
N V M X D I Z C
. . . . .

CPX (Compare X) is a 65x instruction that compares the value of the X index register to something. Internally, this is done via a subtraction, but the difference is not stored anywhere. Thus, the purpose of CPX is to setup the flags. The index register X is the minuend. Depending on the addressing mode used, the subtrahend will be either an immediate value or the value stored at the effective address specified by the operand. The contents at the effective address (when not using immediate data) and the X index register both remain unchanged.

CPX assumes its operands are unsigned.

Syntax

CPX #const
CPX addr
CPX dp

Cycle Penalties

TODO

See Also

External Links