
A-144 SC140 DSP Core Reference Manual
DECGE
DECGE Decrement and Set T DECGE
If Greater Than or Equal to Zero (DALU)
Description
Status and Conditions that Affect Instruction
None.
Status and Conditions Changed by Instruction
Example
decge
Instruction Formats and Opcodes
Note: ** indicates serial grouping encoding.
Operation Assembler Syntax
Dn – 1 → Dn; Dn≥0 → T
DECGE Dn
DECGE Dn
Decrements a data register (Dn) and sets the T bit if the result is greater than or equal to zero. In the case of
an arithmetic overflow (DECGE on the value $80 0000 0000), the T bit will not be set.
Register Address Bit Name Description
SR[0] C Calculates and updates the carry bit in the status register.
SR[1] T Set if result ≥ 0, cleared otherwise.
EMR[2] DOVF Set if the result cannot be represented in 40 bits.
Ln L Clears the Ln bit in the destination register.
Instruction SR d3
move.w #$1,d3 ;$00E4 0000 $00 0000 0001
decge d3 ;$00E4 0002 T-bit set $00 0000 0000
decge d3 ;$00E4 0001 T-bit cleared, carry bit set $FF FFFF FFFF
Instruction Words Cycles Type Opcode
15 8 7 0
DECGE Dn 1 1 1 0*1001FFF1101100
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