MC68HC705P9CDW FREESCALE [Freescale Semiconductor, Inc], MC68HC705P9CDW Datasheet - Page 48

• Manufacturer Part Number: MC68HC705P9CDW
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Central Processor Unit (CPU)
4.6.4 Program Counter
4.6.5 Condition Code Register
Technical Data
48
Reset:
Read:
Write:
Reset:
Read:
Write:
The program counter is a 16-bit register that contains the address of the
next instruction or operand to be fetched. The three most significant bits
of the program counter are ignored internally and appear as 000.
Normally, the address in the program counter automatically increments
to the next sequential memory location every time an instruction or
operand is fetched. Jump, branch, and interrupt operations load the
program counter with an address other than that of the next sequential
location.
The condition code register is an 8-bit register whose three most
significant bits are permanently fixed at 111. The condition code register
contains the interrupt mask and four flags that indicate the results of the
instruction just executed.
H — Half-Carry Flag
The CPU sets the half-carry flag when a carry occurs between bits 3
and 4 of the accumulator during an ADD or ADC operation. The half-
carry flag is required for binary-coded decimal (BCD) arithmetic
operations.
Freescale Semiconductor, Inc.
For More Information On This Product,
Bit
15
0
Bit 7
1
1
14
0
Figure 4-6. Condition Code Register (CCR)
Central Processor Unit (CPU)
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= Unimplemented
13
0
6
1
1
Figure 4-5. Program Counter (PC)
12
11
5
1
1
10
Loaded with vector from $1FFE and $1FFF
9
H
U
4
8
U = Unaffected
7
3
1
I
6
5
MC68HC705P9 — Rev. 4.0
N
U
2
4
3
U
1
Z
2
MOTOROLA
1
Bit 0
C
U
Bit
0