HD6433640 HITACHI [Hitachi Semiconductor], HD6433640 Datasheet - Page 28

• Manufacturer Part Number: HD6433640
• Description: H8/3644 Series Hardware Manual
• Manufacturer: HITACHI [Hitachi Semiconductor]

Condition Code Register (CCR): This 8-bit register contains internal status information,
including the interrupt mask bit (I) and half-carry (H), negative (N), zero (Z), overflow (V), and
carry (C) flags. These bits can be read and written by software (using the LDC, STC, ANDC,
ORC, and XORC instructions). The N, Z, V, and C flags are used as branching conditions for
conditional branching (Bcc) instructions.
Bit 7—Interrupt Mask Bit (I): When this bit is set to 1, interrupts are masked. This bit is set to 1
automatically at the start of exception handling. The interrupt mask bit may be read and written by
software. For further details, see section 3.3, Interrupts.
Bit 6—User Bit (U): Can be used freely by the user.
Bit 5—Half-Carry Flag (H): When the ADD.B, ADDX.B, SUB.B, SUBX.B, CMP.B, or NEG.B
instruction is executed, this flag is set to 1 if there is a carry or borrow at bit 3, and is cleared to 0
otherwise.
The H flag is used implicitly by the DAA and DAS instructions.
When the ADD.W, SUB.W, or CMP.W instruction is executed, the H flag is set to 1 if there is a
carry or borrow at bit 11, and is cleared to 0 otherwise.
Bit 4—User Bit (U): Can be used freely by the user.
Bit 3—Negative Flag (N): Indicates the most significant bit (sign bit) of the result of an
instruction.
Bit 2—Zero Flag (Z): Set to 1 to indicate a zero result, and cleared to 0 to indicate a non-zero
result.
Bit 1—Overflow Flag (V): Set to 1 when an arithmetic overflow occurs, and cleared to 0 at other
times.
Bit 0—Carry Flag (C): Set to 1 when a carry occurs, and cleared to 0 otherwise. Used by:
The carry flag is also used as a bit accumulator by bit manipulation instructions.
Some instructions leave some or all of the flag bits unchanged.
Refer to the H8/300L Series Programming Manual for the action of each instruction on the flag
bits.
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Add instructions, to indicate a carry
Subtract instructions, to indicate a borrow
Shift/rotate carry