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SAM47 INSTRUCTION SET

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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

SBC

SCF

RCF

CCF

RRC

LDB

BAND

BOR

BXOR

IRET

C,(operand)

C,(operand)

C,(operand)

C,(operand)

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

ADC A,@HL

1

ADS A,#im

2

xxx

3

xxx

4

SBC A,@HL

1

ADS A,#im

2

xxx

3

xxx

4

If the result of

instruction 1 is:

Overflow

No overflow

Borrow

No borrow

Then, the execution

sequence is:

1, 3, 4

1, 2, 3, 4

Reason

ADS cannot skip

instruction 3, even if it

has a skip function.

1, 2, 3, 4

1, 3, 4

ADS cannot skip

instruction 3, even if it

has a skip function.



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