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4.6.2.14 CMP
CMP[.W] Compare source word and destination word
CMP.B Compare source byte and destination byte
Syntax
CMP src,dst or CMP.W src,dst
CMP.B src,dst
Operation (.not.src) + 1 + dst
or
dst – src
BIC #2,SR
Emulation
Description The source operand is subtracted from the destination operand. This is made by adding
the 1s complement of the source + 1 to the destination. The result affects only the status
bits in SR.
Register mode: the register bits Rdst.19:16 (.W) resp. Rdst. 19:8 (.B) are not cleared.
Status Bits N: Set if result is negative (src > dst), reset if positive (src = dst)
Z: Set if result is zero (src = dst), reset otherwise (src ≠ dst)
C: Set if there is a carry from the MSB, reset otherwise
V: Set if the subtraction of a negative source operand from a positive destination
operand delivers a negative result, or if the subtraction of a positive source operand
from a negative destination operand delivers a positive result, reset otherwise (no
overflow).
Mode Bits OSCOFF, CPUOFF, and GIE are not affected.
Example Compare word EDE with a 16-bit constant 1800h. Jump to label TONI if EDE equals the
constant. The address of EDE is within PC + 32 K.
CMP #01800h,EDE ; Compare word EDE with 1800h
JEQ TONI ; EDE contains 1800h
... ; Not equal
Example A table word pointed to by (R5 + 10) is compared with R7. Jump to label TONI if R7
contains a lower, signed 16-bit number. R7.19:16 is not cleared. The address of the
source operand is a 20-bit address in full memory range.
CMP.W 10(R5),R7 ; Compare two signed numbers
JL TONI ; R7 < 10(R5)
... ; R7 >= 10(R5)
Example A table byte pointed to by R5 (20-bit address) is compared to the value in output Port1.
Jump to label TONI if values are equal. The next table byte is addressed.
CMP.B @R5+,&P1OUT ; Compare P1 bits with table. R5 + 1
JEQ TONI ; Equal contents
... ; Not equal
177
SLAU144J–December 2004–Revised July 2013 CPUX
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