Section 2 CPU
Rev. 3.00 Mar. 14, 2006 Page 31 of 804
REJ09B0104-0300
Bit Bit
Name
Initial
Value R/W
Description
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, this 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, this 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 (regarded as
sign bit) of data.
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.
0 C
Undefined
R/W
Carry
Flag
Set to 1 when a carry occurs, and cleared to 0
otherwise. A carry has the following types:
•
Carry from the result of addition
•
Borrow from the result of subtraction
•
Carry from the result of shift or rotation
The carry flag is also used as a bit accumulator by bit
manipulation instructions.
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Содержание H8SX series
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