mc68hc908gp20 Freescale Semiconductor, Inc, mc68hc908gp20 Datasheet - Page 156

• Manufacturer Part Number: mc68hc908gp20
• Description: M68hc08 Family Of 8-bit Microcontroller Units Mcus
• Manufacturer: Freescale Semiconductor, Inc

10.4.5 Condition Code Register
Advance Information
156
The 8-bit condition code register contains the interrupt mask and five
flags that indicate the results of the instruction just executed. Bits 6 and
5 are set permanently to logic 1. The following paragraphs describe the
functions of the condition code register.
V — Overflow Flag
H — Half-Carry Flag
Reset:
Read:
Write:
The CPU sets the overflow flag when a two's complement overflow
occurs. The signed branch instructions BGT, BGE, BLE, and BLT use
the overflow flag.
The CPU sets the half-carry flag when a carry occurs between
accumulator bits 3 and 4 during an add-without-carry (ADD) or add-
with-carry (ADC) operation. The half-carry flag is required for binary-
coded decimal (BCD) arithmetic operations. The DAA instruction uses
the states of the H and C flags to determine the appropriate correction
factor.
1 = Overflow
0 = No overflow
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
X = Indeterminate
Bit 7
V
X
Figure 10-6. Condition Code Register (CCR)
6
1
1
5
1
1
H
X
4
3
1
I
MC68HC908GP20
Freescale Semiconductor
N
X
2
X
1
Z
—
Rev 2.1
Bit 0
C
X