H8S2245 datasheet(73/818 Pages) RENESAS

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Section 2 CPU

Rev.3.00 Mar. 26, 2007 Page 31 of 772

REJ09B0355-0300

(3) Condition-Code Register (CCR)

This 8-bit register contains internal CPU status information, including an interrupt mask bit (I) and

half-carry (H), negative (N), zero (Z), overflow (V), and carry (C) flags.

Bit 7—Interrupt Mask Bit (I): Masks interrupts other than NMI when set to 1. (NMI is accepted

regardless of the I bit setting.) The I bit is set to 1 by hardware at the start of an exception-

handling sequence. For details, refer to section 5, Interrupt Controller.

Bit 6—User Bit or Interrupt Mask Bit (UI): Can be written and read by software using the

LDC, STC, ANDC, ORC, and XORC instructions. This bit can also be used as an interrupt mask

bit. For details, refer to section 5, Interrupt Controller.

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 cleared to 0

otherwise. When the ADD.W, SUB.W, CMP.W, or NEG.W instruction is executed, the H flag is

set to 1 if there is a carry or borrow at bit 11, and cleared to 0 otherwise. When the ADD.L,

SUB.L, CMP.L, or NEG.L instruction is executed, the H flag is set to 1 if there is a carry or

borrow at bit 27, and cleared to 0 otherwise.

Bit 4—User Bit (U): Can be written and read by software using the LDC, STC, ANDC, ORC, and

XORC instructions.

Bit 3—Negative Flag (N): Stores the value of the most significant bit (sign bit) of data.

Bit 2—Zero Flag (Z): Set to 1 to indicate zero data, and cleared to 0 to indicate non-zero data.

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 and rotate instructions, to indicate a carry

The carry flag is also used as a bit accumulator by bit manipulation instructions.

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