Samsung S3C8275X - Manual (Page 164)

INSTRUCTION SET S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
6-30
CP
— Compare
CP dst,src
Operation: dst – src
The source operand is compared to (subtracted from) the destination operand, and the
appropriate flags are set accordingly. The contents of both operands are unaffected by the
comparison.
Flags: C: Set if a "borrow" occurred (src > dst); cleared otherwise.
Z: Set if the result is "0"; cleared otherwise.
S: Set if the result is negative; cleared otherwise.
V: Set if arithmetic overflow occurred; cleared otherwise.
D: Unaffected.
H: Unaffected.
Format:
Bytes Cycles Opcode
(Hex)
Addr Mode
dst src
opc dst | src 2 4 A2 r r
6 A3 r lr
opc src dst 3 6 A4 R R
6 A5 R IR
opc dst src 3 6 A6 R IM
Examples: 1. Given: R1 = 02H and R2 = 03H:
CP R1,R2
→
Set the C and S flags
Destination working register R1 contains the value 02H and source register R2 contains the value
03H. The statement "CP R1,R2" subtracts the R2 value (source/subtrahend) from the R1 value
(destination/minuend). Because a "borrow" occurs and the difference is negative, C and S are
"1".
2. Given: R1 = 05H and R2 = 0AH:
CP R1,R2
JP UGE,SKIP
INC R1
SKIP LD R3,R1
In this example, destination working register R1 contains the value 05H which is less than the
contents of the source working register R2 (0AH). The statement "CP R1,R2" generates C = "1"
and the JP instruction does not jump to the SKIP location. After the statement "LD R3,R1"
executes, the value 06H remains in working register R3.