XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 64

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

Central Processor Unit (CPU)
3.3.4 Stack Pointer
3.3.5 Program Counter
Data Sheet
64
Reset:
Reset:
Read:
Read:
Write:
Write:
Bit 15
Bit 15
SP15
SP15
NOTE:
SP14
SP14
14
14
SP13
SP13
13
13
The stack pointer (SP) contains the last stack address used. The CPU12 supports
an automatic program stack that is used to save system context during subroutine
calls and interrupts.
The stack pointer can also serve as a temporary data storage location or as an
index register for indexed addressing.
The LDS and STS instructions can be used to manipulate data in and out of the
stack pointer.
The program counter contains the address of the next instruction to be executed.
The program counter can also serve as an index register in all indexed addressing
modes except autoincrement and autodecrement.
SP12
SP12
12
12
SP11
SP11
11
11
Figure 3-8. Program Counter (PC)
Figure 3-7. Stack Pointer (SP)
SP10
SP10
10
10
Central Processor Unit (CPU)
SP9
SP9
9
9
Unaffected by reset
Unaffected by reset
SP8
SP8
8
8
SP7
SP7
7
7
SP6
SP6
6
6
SP5
SP5
5
5
SP4
SP4
4
4
M68HC12B Family — Rev. 8.0
SP3
SP3
3
3
SP2
SP2
2
2
SP1
SP1
MOTOROLA
1
1
Bit 0
Bit 0
SP0
SP0