Texas Instruments TMS320C28x Reference Manual page 495

SUB AX, loc16
SUB AX, loc16
SYNTAX OPTIONS
SUB AX, loc16
Operands AX
loc16
Description
Flags and N
Modes
Z
C
V
Repeat
Example
; Subtract the contents of VarA with VarB and store in VarC
MOV
SUB
MOV
6-338
1001 111A LLLL LLLL
Accumulator high (AH) or accumulator low (AL) register
Addressing mode (see Chapter 5)
Subtract the 16−bit content of the location pointed to by the "loc16"
addressing mode from the specified AX register (AH or AL) and store the
results in AX:
AX = AX − [loc16];
After the subtraction, AX is tested for a negative condition. If bit 15 of AX is 1,
then the negative flag bit is set; otherwise it is cleared.
After the subtraction, AX is tested for a zero condition. The zero flag bit is set
if the operation generates AX = 0, otherwise it is cleared
If the subtraction generates a borrow, C is cleared; otherwise C is set.
If an overflow occurs, V is set; otherwise V is not affected. Signed positive
overflow occurs if the result crosses the max positive value (0x7FFF) in the
positive direction. Signed negative overflow occurs if the result crosses the
max negative value (0x8000) in the negative direction.
This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
AL,@VarA
AL,@VarB
@VarC,AL
Subtract Specified Location From AX
OPCODE
; Load AL with contents of VarA
; Subtract from AL contents of VarB
; Store result in VarC
OBJMODE RPT CYC
X − 1