Texas Instruments TMS320C28x, Reference Manual

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SUBB ACC,#8bit
6-340
SUBB ACC,#8bit Subtract 8-bit Value
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
SUBB ACC,#8bit
0001 1001 CCCC CCCC
X − 1
Operands ACC Accumulator register
#8bit 8-bit immediate constant value
Description Subtract the zero − extended, 8-bit constant from the ACC register:
ACC = ACC − 0:8bit;
Flags and
Z
After the subtraction, the Z flag is set if ACC is zero, else Z is cleared. g
Modes
N After the subtraction, the N flag is set if bit 31 of the ACC is 1, N is cleared.
C If the subtraction generates a borrow, C is cleared; otherwise C is set.
V If an overflow occurs, V is set; otherwise, V is not affected.
OVC
If(OVM = 0, disabled) then if the operation generates a positive overflow,
then the counter is incremented and if the operation generates a negative
overflow, then the counter is decremented. If(OVM = 1, enabled) then the
counter is not affected by the operation.
OVM If overflow mode bit is set; then the ACC value will saturate maximum
positive (0x7FFFFFFF) or maximum negative (0x80000000) if the operation
overflowed.
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example
; Decrement contents of 32-bit location VarA:
MOVL ACC,@VarA ; Load ACC with contents of VarA
SUBB ACC,#1 ; Subtract 1 from ACC
MOVL @VarA,ACC ; Store result back into VarA