INSTRUCTIONS WHICH AFFECT THE CARRY FLAG

The only instructions which do not generate a skip signal, but which do affect the carry flag are as follows:

ADC

LDB

C,(operand)

SBC

BAND

C,(operand)

SCF

BOR

C,(operand)

RCF

BXOR

C,(operand)

CCF

IRET

RRC

ADC AND SBC INSTRUCTION SKIP CONDITIONS

The instructions 'ADC A,@HL' and 'SBC A,@HL' can generate a skip signal, and set or clear the carry flag, when

they are executed in combination with the instruction 'ADS A,#im'.

If an 'ADS A,#im' instruction immediately follows an 'ADC A,@HL' or 'SBC A,@HL' instruction in a program

sequence, the ADS instruction does not skip the instruction following ADS, even if it has a skip function. If,

however, an 'ADC A,@HL' or 'SBC A,@HL' instruction is immediately followed by an 'ADS A,#im' instruction, the

ADC (or SBC) skips on overflow (or if there is no borrow) to the instruction immediately following the ADS, and

program execution continues. Table 5-3 contains additional information and examples of the 'ADC A,@HL' and

'SBC A,@HL' skip feature.

Table 5-3. Skip Conditions for ADC and SBC Instructions

Sample

Instruction Sequences

If the result of

instruction 1 is:

Then, the execution

sequence is:

Reason

ADC A,@HL

ADS A,#im

xxx

xxx

1

2

3

4

Overflow

No overflow

1, 3, 4

1, 2, 3, 4

ADS cannot skip

instruction 3, even if it

has a skip function.

SBC A,@HL

ADS A,#im

xxx

xxx

1

2

3

4

Borrow

No borrow

1, 2, 3, 4

1, 3, 4

ADS cannot skip

instruction 3, even if it

has a skip function.