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Rev. 1.00, 05/04, page 24 of 544
2.4.4 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. Operations can be
performed on the CCR bits by the LDC, STC, ANDC, ORC, and XORC instructions. The N, Z, V,
and C flags are used as branching conditions for conditional branch (Bcc) instructions.
Bit Bit Name
Initial
Value R/W Description
7 I 1 R/W Interrupt Mask Bit
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 at the start of an exception-handling sequence. For
details, refer to section 5, Interrupt Controller.
6 UI Undefined R/W User Bit or Interrupt Mask Bit
Can be written to and read from by software using the
LDC, STC, ANDC, ORC, and XORC instructions.
5 H Undefined R/W Half-Carry Flag
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.
4 U Undefined R/W User Bit
Can be written to and read from by software using the
LDC, STC, ANDC, ORC, and XORC instructions.
3 N Undefined R/W Negative Flag
Stores the value of the most significant bit of data as a
sign bit.
2 Z Undefined R/W Zero Flag
Set to 1 to indicate zero data, and cleared to 0 to
indicate non-zero data.
1 V Undefined R/W Overflow Flag
Set to 1 when an arithmetic overflow occurs, and
cleared to 0 otherwise.