S3C72P9 datasheet(35/225 Pages) SAMSUNG

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S3C72P9/P72P9 (Preliminary Spec)

ADDRESS SPACES

2-23

SKIP CONDITION FLAGS (SC2, SC1, SC0)

The skip condition flags SC2, SC1, and SC0 in the PSW indicate the current program skip conditions and are set

and reset automatically during program execution. Skip condition flags can only be addressed by 8-bit read

instructions. Direct manipulation of the SC2, SC1, and SC0 bits is not allowed.

CARRY FLAG (C)

The carry flag is used to save the result of an overflow or borrow when executing arithmetic instructions involving

a carry (ADC, SBC). The carry flag can also be used as a 1-bit accumulator for performing Boolean operations

involving bit-addressed data memory.

If an overflow or borrow condition occurs when executing arithmetic instructions with carry (ADC, SBC), the carry

flag is set to "1". Otherwise, its value is "0". When a

RESET occurs, the current value of the carry flag is retained

during power-down mode, but when normal operating mode resumes, its value is undefined.

The carry flag can be directly manipulated by predefined set of 1-bit read/write instructions, independent of other

bits in the PSW. Only the ADC and SBC instructions, and the instructions listed in Table 2-7, affect the carry flag.

Table 2-7. Valid Carry Flag Manipulation Instructions

Operation Type

Instructions

Carry Flag Manipulation

Direct manipulation

SCF

Set carry flag to "1".

RCF

Clear carry flag to "0" (reset carry flag).

CCF

Invert carry flag value (complement carry flag).

BTST C

Test carry and skip if C = "1".

Bit transfer

LDB (operand) (1),C

Load carry flag value to the specified bit.

LDB C,(operand) (1)

Load contents of the specified bit to carry flag.

Boolean manipulation

BAND C,(operand) (1)

AND the specified bit with contents of carry flag and save

the result to the carry flag.

BOR C,(operand) (1)

OR the specified bit with contents of carry flag and save

the result to the carry flag.

BXOR C,(operand) (1)

XOR the specified bit with contents of carry flag and save

the result to the carry flag.

Interrupt routine

INTn (2)

Save carry flag to stack with other PSW bits.

Return from interrupt

IRET

Restore carry flag from stack with other PSW bits.

NOTES:

The operand has three bit addressing formats: mema.a, memb.@L, and @H + DA.b.

'INTn' refers to the specific interrupt being executed and is not an instruction.

S3C72P9 Datasheet(PDF) 35 Page - Samsung semiconductor

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