Texas Instruments TMS320C28x Reference Manual page 496

SUB loc16, AX
SYNTAX OPTIONS
SUB loc16, AX
Operands loc16
AX
Description
Flags and N
Modes
Z
C
V
Repeat
Example
; Subtract the contents of VarA from index register AR0:
MOV
SUB
; Subtract the contents of VarB from VarC:
MOV
SUB
0111 010A LLLL LLLL
Addressing mode (see Chapter 5)
Accumulator high (AH) or accumulator low (AL) register
Subtract the content of the specified AX register (AH or AL) from the 16-bit
content of the location pointed to by the "loc16" addressing mode and store
the result in location pointed to by "loc16":
[loc16] = [loc16] − AX;
After the subtraction, [loc16] is tested for a negative condition. If bit 15 of
[loc16]
is 1, then the negative flag bit is set; otherwise it is cleared.
After the subtraction, [loc16] is tested for a zero condition. The zero flag bit is
set if the operation generates [loc16] = 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
@AR0,AL
AH,@VarB
@VarC,AH
Reverse-Subtract Specified Location From AX
OPCODE
; Load AL with contents of VarA
; AR0 = AR0 − AL
; Load AH with contents of VarB
; VarC = VarC − AH
SUB loc16, AX
OBJMODE RPT CYC
X − 1
6-339