dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 465

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

DECA.L
Operation:
D – 2 → D
Description: Decrement a value in an AGU pointer register by two. The full 24-bit value of the pointer register is
Usage:
Example:
Explanation of Example:
Condition Codes Affected:
Instruction Fields:
Instruction Opcodes:
Timing:
Memory:
Freescale Semiconductor
DECA.L Rn
Operation
DECA.L
Before Execution
R0
used when decrementing.
This instruction is used to step backwards through a memory buffer that is composed of long-word val-
ues. Since each long word consists of 2 words, this instruction can be used to step through a buffer by
every other word.
DECA.L R0
Prior to execution, the R0 register contains $002222. Execution of the DECA.L R0 instruction causes
the value in the R0 to be reduced by two, and the result ($002220) is stored back in R0.
The condition codes are not modified by this instruction.
1 oscillator clock cycle
1 program word
(no parallel move)
Operands
002222
Rn
Decrement Long in AGU Register
15
1
C
1
Instruction Set Details
0
; decrement R0 by 2
W
1
0
Assembler Syntax:
DECA.L
Decrement AGU register by two
12
0
11
0
After Execution
R0
1
0
D
0
8
002220
Comments
7
1
(no parallel move)
0
1
1
4
DECA.L
R
3
1
R
A-121
R
0