INSTRUCTION SET S3C84E5/C84E9/P84E9
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
The destination working register R1 contains the value 02H and the 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, the C and
the S flag values are "1".
2. Given: R1 = 05H and R2 = 0AH:
CP R1,R2
JP UGE,SKIP
INC R1
SKIP LD R3,R1
In this example, the 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 the working register R3.