dsp56000 Freescale Semiconductor, Inc, dsp56000 Datasheet - Page 338

• Manufacturer Part Number: dsp56000
• Description: 24-bit Digital Signal Processor Family Manual
• Manufacturer: Freescale Semiconductor, Inc

Operation:
Description: Subtract the source one operand, S1, from the source two accumulator,
S2, and update the condition code register. The result of the subtraction operation is not
stored.
Note:
sign extended and zero filled to form a valid 56-bit operand. For the carry to be set cor-
rectly as a result of the subtraction, S2 must be properly sign extended. S2 can be
improperly sign extended by writing A1 or B1 explicitly prior to executing the compare so
that A2 or B2, respectively, may not represent the correct sign extension. This note par-
ticularly applies to the case where it is extended to compare 24-bit operands such as X0
with A1.
Example:
Explanation of Example: Prior to execution, the 56-bit B accumulator contains the
value $00:000020:000000 and the 24-bit Y0 register contains the value $000024. The
execution of the CMP Y0,B instruction automatically appends the 24-bit value in the Y0
register with 24 LS zeros, sign extends the resulting 48-bit long word to 56 bits, subtracts
the result from the 56-bit B accumulator and updates the condition code register.
A - 72
CMP
S2 – S1(parallel move)
CMP Y0,B
This instruction subtracts 56-bit operands. When a word is specified as S1, it is
Y0
SR
B
:
:
$00:000020:000000
Before Execution
X0,X:(R6)+N6
Freescale Semiconductor, Inc.
For More Information On This Product,
$000024
INSTRUCTION DESCRIPTIONS
$0300
INSTRUCTION SET DETAILS
Go to: www.freescale.com
Compare
Y1,Y:(R0)–
Assembler Syntax:
SR
Y0
B
CMP
;comp. Y0 and B, save X0, Y1
$00:000020:000000
After Execution
S1, S2 (parallel move)
$000024
$0319
MOTOROLA
CMP