MC68HC908AZ32ACFU MOTOROLA [Motorola, Inc], MC68HC908AZ32ACFU Datasheet - Page 98

• Manufacturer Part Number: MC68HC908AZ32ACFU
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Central Processor Unit (CPU)
6.4.3 Stack pointer (SP)
Advance Information
98
NOTE:
H:X
SP
Reset:
Reset:
Read:
Read:
Write:
Write:
In the indexed addressing modes, the CPU uses the contents of the
index register to determine the conditional address of the operand.
The index register can also be used as a temporary data storage
location.
The stack pointer is a 16-bit register that contains the address of the next
location on the stack. During a reset, the stack pointer is preset to
$00FF. The reset stack pointer (RSP) instruction sets the least
significant byte to $FF and does not affect the most significant byte. The
stack pointer decrements as data is pushed onto the stack and
increments as data is pulled from the stack.
In the stack pointer 8-bit offset and 16-bit offset addressing modes, the
stack pointer can function as an index register to access data on the
stack. The CPU uses the contents of the stack pointer to determine the
conditional address of the operand.
The location of the stack is arbitrary and may be relocated anywhere in
RAM. Moving the SP out of page zero ($0000 to $00FF) frees direct
address (page zero) space. For correct operation, the stack pointer must
point only to RAM locations.
Freescale Semiconductor, Inc.
X = Indeterminate
For More Information On This Product,
Bit
15
Bit
15
0
0
14
14
0
0
Central Processor Unit (CPU)
Go to: www.freescale.com
13
13
Figure 6-3. Index register (H:X)
0
0
12
12
0
0
11
11
0
0
10
10
0
0
9
0
9
0
8
0
8
0
X
7
7
1
X
6
6
1
X
5
5
1
68HC908AZ32A — Rev 0.0
X
4
4
1
X
3
3
1
2
X
2
1
MOTOROLA
X
1
1
1
Bit
Bit
X
0
0
1