DECEQA

 

 

DECEQA Decrement and Set T If Equal Zero DECEQA

 

 

(AGU)

Operation

Assembler Syntax

Rx – 1 → Rx; if Rx==0, then 1 → T, else 0 → T DECEQA Rx

Description

DECEQA Rx

Decrements an AGU register (Rx) and sets the T bit if the result is zero. SP cannot be used as an operand of this instruction.

Status and Conditions that Affect Instruction

None.

Status and Conditions Changed by Instruction

Register Address

Bit Name

Description

SR[1]

T

Set if result = 0, cleared otherwise.

Example

deceqa r0

Register/Memory Address

R0

SR

Before

$0000 0001

$00E4 0000

After

$0000 0000

$00E4 0002

Instruction Formats and Opcodes

Instruction

Words

Cycles

Type

DECEQA Rx

1

1

2

Opcode

158 70

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

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. SP cannot be used as an operand for this instruction.

SC140 DSP Core Reference Manual

A-143

Page 457
Image 457
Freescale Semiconductor SC140 specifications Deceqa Decrement and Set T If Equal Zero Deceqa, Deceqa r0, Deceqa Rx