Texas Instruments TMS320C28x Reference Manual page 231

CMP AX, loc16
CMP AX, loc16
SYNTAX OPTIONS
CMP AX, loc16
Operands AX
loc16
Description
Flags N
and
Modes
Z
C
Repeat
Example
; Branch if VarA is higher then VarB:
MOV
CMPB
SB
6-74
Accumulator high (AH) or accumulator low (AL) register
Addressing mode (see Chapter 5)
The content of the specified AX register (AH or AL) is compared with the 16-bit
content of the location pointed to by the "loc16" addressing mode. The result
of (AX−- [loc16] ) is evaluated and the status flag bits set accordingly. The AX
register and content of the location pointed to by "loc16" are left unchanged:
Set Flags On (AX − [loc16]);
If the result of the operation is negative, then N is set; otherwise it is cleared.
The CMP instruction assumes infinite precision when it determines the sign of
the result. For example, consider the subtraction 0x8000 − 0x0001. If the
precision were limited to 16 bits, the result would cause an overflow to the
positive number 0x7FFF and N would be cleared. However, because the CMP
instruction assumes infinite precision, it would set N to indicate that
0x8000 − 0x0001 actually results in a negative number.
The comparison is tested for a zero condition. The zero flag bit is set if the
operation ( AX − [loc16] ) = 0, otherwise it is cleared.
If the subtraction generates a borrow, then C is cleared; otherwise C is set.
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
Dest,HI
OPCODE
0101 010A LLLL LLLL
; Load AL with contents of VarA
; Set Flags On (AL − VarB)
; Branch if VarA higher then VarB
Compare
OBJMODE RPT CYC
X − 1