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CHAPTER 3 REGISTER DESCRIPTIONS
■ Condition Code Register (CCR: Bit 07 to bit 00)
● Bit Configuration of the "CCR"
Figure 3.3-6 Bit Configuration of the "CCR"
● "CCR" Functions
•"S" Flag
This flag selects the stack pointer to be used. The value "0" selects the system stack pointer (SSP), and
"1" selects the user stack pointer (USP).
RETI instruction is executable only when the S flag is "0".
•"I" Flag
This flag is used to enable/disable system interrupts. The value "0" disables, and "1" enables interrupts.
•"N" Flag
This flag is used to indicate positive or negative values when the results of a calculation are expressed in
two’s complement form. The value "0" indicates positive, and "1" indicates negative.
•"Z" Flag
This flag indicates whether the results of a calculations are zero. The value "0" indicates a non-zero
value, and "1" indicates a zero value.
•"V" Flag
This flag indicates that an overflow occurred when the results of a calculation are expressed in two’s
complement form. The value "0" indicates no overflow, and "1" indicates an overflow.
•"C" Flag
This flag indicates whether a carry or borrow condition has occurred in the highest bit of the results of a
calculation. The value "0" indicates no carry or borrow, and "1" indicates a carry or borrow condition.
This bit is also used with shift instructions, and contains the value of the last bit that is "shifted out".
● Initialization of the "CCR" at Reset
Following a reset, the "S" and "I" flags are set to "0" and the "N", "Z", "V" and "C" flags are undefined.
CCR - -
SINZVC
07 06 05 04 03 02 01 00
Initial value: --00XXXXB