mc68hc05pv8a Freescale Semiconductor, Inc, mc68hc05pv8a Datasheet - Page 46

• Manufacturer Part Number: mc68hc05pv8a
• Description: Mc68hc05pv8a Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Technical Data
3.2.4 Program Counter
3.2.5 Condition Code Register
Technical Data
Reset
Reset
Bit 15 14
–
–
The program counter is a 16-bit register that contains the address of the
next instruction or operand to be fetched. The two most significant bits
of the program counter are ignored internally.
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. The following paragraphs describe the
functions of the condition code register.
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.
Bit 7
Freescale Semiconductor, Inc.
1
1
–
–
For More Information On This Product,
13
Figure 3-6 Condition Code Register
6
1
1
12
CPU and Instruction Set
Go to: www.freescale.com
Figure 3-5 Program Counter
11
5
1
1
10
Loaded with vector from $3FFE AND $3FFF
9
H
U
4
8
7
3
1
I
6
MC68HC(8)05PV8/A — Rev. 1.9
5
N
U
2
4
3
C
U
1
2
1
Bit 0
Z
U
Bit 0