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NOTE:
10.4.4 Program Counter
MC68HC908GP32
MC68HC08GP32
•
MOTOROLA
Freescale Semiconductor, Inc.
Bit
14
13
12
15
Read:
Write:
Reset:
0
0
0
0
Figure 10-4. Stack Pointer (SP)
The location of the stack is arbitrary and may be relocated anywhere in
RAM. Moving the SP out of page 0 ($0000 to $00FF) frees direct
address (page 0) space. For correct operation, the stack pointer must
point only to RAM locations.
The program counter is a 16-bit register that contains the address of the
next instruction or operand to be fetched.
Normally, 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.
During reset, the program counter is loaded with the reset vector
address located at $FFFE and $FFFF. The vector address is the
address of the first instruction to be executed after exiting the reset state.
Bit
14
13
12
15
Read:
Write:
Reset:
Figure 10-5. Program Counter (PC)
Rev. 6
—
Central Processor Unit (CPU)
For More Information On This Product,
Go to: www.freescale.com
11
10
9
8
7
6
0
0
0
0
1
1
11
10
9
8
7
6
Loaded with Vector from $FFFE and $FFFF
Central Processor Unit (CPU)
CPU Registers
5
4
3
2
1
1
1
1
1
1
5
4
3
2
1
Technical Data
Bit
0
1
Bit
0
151
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