Renesas H8 Series Hardware Manual page 44

Section 2 CPU
Bit Bit Name
7 I
6 UI
5 H
4 U
3 N
2 Z
1 V
0 C
Rev. 1.00 Aug. 28, 2006 Page 14 of 400
REJ09B0268-0100
Initial
Value R/W
1 R/W
Undefined R/W
Undefined R/W
Undefined R/W
Undefined R/W
Undefined R/W
Undefined R/W
Undefined R/W
Description
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.
User Bit
Can be written and read by software using the LDC,
STC, ANDC, ORC, and XORC instructions.
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.
User Bit
Can be written and read by software using the LDC,
STC, ANDC, ORC, and XORC instructions.
Negative Flag
Stores the value of the most significant bit of data as a
sign bit.
Zero Flag
Set to 1 to indicate zero data, and cleared to 0 to
indicate non-zero data.
Overflow Flag
Set to 1 when an arithmetic overflow occurs, and
cleared to 0 at other times.
Carry Flag
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.