S3F84B8_UM_REV 1.00 6 INSTRUCTION SET
6-29
6.3.17 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 remain 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 source register R2 contains the
value 03H. The statement “CP R1,R2” subtracts R2 value (source/subtrahend) from R1 value
(destination/minuend). When “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, the destination working register R1 contains the value 05H, which is less than the
contents of source working register R2 (0AH). The statement “CP R1,R2” generates C = “1” and
the JP instruction does not jump to SKIP location. Once the statement “LD R3,R1” is executed,
the value 06H remains in working register R3.
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