Cp Compare - Samsung S3C80A5B User Manual

INSTRUCTION SET
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:
opc
opc
opc
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
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.
6-30
dst | src
src dst
dst src
LD R3,R1
Bytes Cycles Opcode
2 4
6
3 6
6
3 6
S3C80A5B
Addr Mode
(Hex) dst src
A2 r r
A3 r lr
A4 R R
A5 R IR
A6 R IM