ADDRESS SPACES KS57C2308/P2308/C2316/P2316
2-20
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:
1. The operand has three bit addressing formats: mema.a, memb.@L, and @H + DA.b.
2. INTn refers to the specific interrupt being executed and is not an instruction.