HD64F3642AHV Datasheet, PDF (41/551 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 2 CPU
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 3VNegative 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:
• Add instructions, to indicate a carry
• Subtract instructions, to indicate a borrow
• Shift/rotate carry
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.
Rev. 6.00 Sep 12, 2006 page 19 of 526
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