MC68HC705P9CDW FREESCALE [Freescale Semiconductor, Inc], MC68HC705P9CDW Datasheet - Page 47

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

4.6.3 Stack Pointer
MC68HC705P9 — Rev. 4.0
MOTOROLA
Reset:
Read:
Write:
The stack pointer is a 16-bit register that contains the address of the next
stack location to be used. During a reset or after the reset stack pointer
instruction (RSP), the stack pointer is preset to $00FF. The address in
the stack pointer decrements after a byte is stacked and increments
before a byte is unstacked.
The 10 most significant bits of the stack pointer are permanently fixed at
0000000011, so the stack pointer produces addresses from $00C0 to
$00FF. If subroutines and interrupts use more than 64 stack locations,
the stack pointer wraps around to address $00FF and begins writing
over the previously stored data. A subroutine uses two stack locations;
an interrupt uses five locations.
Freescale Semiconductor, Inc.
For More Information On This Product,
Bit
15
0
0
= Unimplemented
14
0
0
Central Processor Unit (CPU)
Go to: www.freescale.com
13
0
0
12
0
0
Figure 4-4. Stack Pointer (SP)
11
0
0
10
0
0
9
0
0
8
0
0
7
1
1
6
1
1
Central Processor Unit (CPU)
5
1
4
1
3
1
Technical Data
CPU Registers
2
1
1
1
Bit
0
1
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