Zilog Z16F2810 - Manual (Page 165)

UM018809-0611 SBC Instruction
ZNEO
®
CPU Core
User Manual
149
SBC
Definition
Subtract with Carry
Syntax
SBC dst, src
Operation
dst
 dst
– src – C
Description
This instruction subtracts the source operand and the Carry ( C ) flag from the destination. The
result is stored in the destination address or register. The contents of the source operand are unaf-
fected. The ZNEO CPU performs subtraction by adding the two’s-complement of the source
operand to the destination operand. This instruction is used in multiple-precision arithmetic to
include the carry (borrow) from the subtraction of low-order operands into the subtraction of
high-order operands.
The Zero flag is set only if the initial state of the Zero flag is 1 and the result is 0.
This instruction is generated by using the Extend prefix, 0007H, with the SUB opcodes.
Flags
7 6 5 4 3 2 1 0
C Z S V B CIRQE IRQE
* * * * * – – –
Legend
C = Set to 1 if the result generated a borrow; otherwise set to 0.
Z = Set to 1 if Z is initially 1 and the result is zero; otherwise set to 0.
S = Set to 1 if the result msb is 1; otherwise set to 0.
V = Set to 1 if an arithmetic overflow occurs; otherwise set to 0.
B = Set to 1 if the initial destination or source value is 0; otherwise set to 0.
CIRQE = No change.
IRQE = No change.