ASRA

ASRA

Arithmetic Shift Right

 

By One Bit (AGU)

Operation

Assembler Syntax

Rx>>1 → Rx

ASRA Rx

ASRA

Description

ASRA Rx

Performs an arithmetic right shift by one bit on the AGU register (Rx). Moves bits [31:1] into bits [30:0]. Bit 31 remains the same, creating a sign-extension.

Status and Conditions that Affect Instruction

Register Address

Bit Name

Description

SR[18]

EXP

Determines which stack pointer is used when the stack pointer is an

 

 

operand. Otherwise, the instruction is not affected by SR.

Status and Conditions Changed by Instruction

None.

Example

asra r2

Register/Memory Address

R2

Before

$8002 0002

After

$C001 0001

Instruction Formats and Opcodes

Instruction

Words

Cycles

Type

ASRA Rx

1

1

2

Opcode

158 70

1 1 1 0 R R R R 1 1 1 1 1 1 0 1

Instruction Fields

Rx

RRRR

AGU Source/Destination Register

 

 

 

 

 

0000

N0

0100

1000

R0

1100

R4

 

 

 

 

 

 

 

 

 

 

0001

N1

0101

1001

R1

1101

R5

 

 

 

 

 

 

 

 

 

 

0010

N2

0110

1010

R2

1110

R6

 

 

 

 

 

 

 

 

 

 

0011

N3

0111

SP

1011

R3

1111

R7

 

 

 

 

 

 

 

 

Note:

This instruction

can specify R8-R15 as operands by using a high register prefix.

 

SC140 DSP Core Reference Manual

A-59

Page 373
Image 373
Freescale Semiconductor SC140 specifications Asra r2, Asra Rx