HD64F3687HV Datasheet, PDF (52/538 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series

Section 2 CPU
Initial
Bit
Bit Name 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.
6
UI
Undefined R/W User Bit
Can be written and read 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 and read 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 at other times.
0
C
Undefined R/W 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.
Rev.5.00 Nov. 02, 2005 Page 18 of 500
REJ09B0027-0500