Decgea, Decrement and set t, Example 2 – Freescale Semiconductor StarCore SC140 User Manual
Page 460: Operation assembler syntax
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SC140 DSP Core Reference Manual
DECGEA
DECGEA
Decrement and Set T
DECGEA
If Greater Than or Equal to Zero (AGU)
Description
Status and Conditions that Affect Instruction
None.
Status and Conditions Changed by Instruction
Example 1
decgea r4
Example 2
decgea r4
Operation
Assembler Syntax
Rx – 1
→ Rx; Rx ≥ 0 → T
DECGEA Rx
DECGEA Rx
Decrements an AGU register (Rx) and sets the T bit if the result is greater than or equal to zero. In case
there is an arithmetic overflow (DECGEA on the value of $80000000), the T bit will not be set by this
instruction. SP cannot be used as an operand of this instruction.
Register Address
Bit Name
Description
SR[1]
T
Set if result
≥ 0, cleared otherwise.
Register/Memory Address
Before
After
R4
$0010 E438
$0010 E437
SR
$00E4 0000
$00E4 0002
Register/Memory Address
Before
After
R4
$8000 0000
$7FFF FFFF
SR
$00E4 0002
$00E4 0000