dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 108

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

Instruction Set Introduction
Note that the alternate syntax is merely an alias to the regular instruction syntax. When dis-assembled, the
instruction appears with the standard syntax, with the register operand repeated.
4.2.2.2
When an instruction operand uses the index-by-6-bit-displacement or index-by-3-bit-displacement
addressing modes, the DSP56800E assembler examines the effective address calculation to see if the
operand can be mapped to one that uses a simpler addressing mode. Specifically, when the assembler
detects occurrences of the following addressing modes, it remaps them:
In both cases, the operand addressing mode is remapped to the X:(SP) addressing mode.
4.3
One particular class of instructions merits additional attention: the delayed flow control instructions. These
instructions are designed to increase throughput by eliminating execution cycles that are wasted when
program flow changes.
An instruction that affects normal program flow (such as branch or jump instruction) requires 2 or 3
additional instruction cycles to flush the execution pipeline. The program controller stops fetching
instructions at the current location and begins to fill the pipeline from the target address. The execution
pipeline is said to stall while this switch occurs. The additional cycles required to flush the pipeline are
4-12
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•
X:(SP–xx) where the value of the 6-bit offset is “0”
X:(SP–x) where the value of the 3-bit offset is “0”
Delayed Flow Control Instructions
ADDA
ADDA.L
ASL16
ASLA
ASR16
LSR16
SAT
SXT.B
SXT.L
ZXT.B
Addressing Mode Remapping
Operation
Standard Syntax
Table 4-12. Instructions with Alternate Syntax
#xxxx,Rn,Rn
#xxxx,Rn,Rn
FFF,FFF
FFF,FFF
FFF,FFF
FF,FFF
#xxxxxx,Rn,Rn
#xxxxxx,Rn,Rn
Rn,Rn
FFF,FFF
FF,FFF
FFF,FFF
DSP56800E Core Reference Manual
Operands
ADDA
ADDA.L
ASL16
ASLA
ASR16
LSR16
SAT
SXT.B
SXT.L
ZXT.B
Operation
Alternate Syntax
#xxxx,Rn
#xxxxxx,Rn
#xxxx,Rn
#xxxxxx,Rn
FFF
Rn
FFF
FFF
FF
FFF
FF
FFF
Operands
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