mc68hc705k1 Freescale Semiconductor, Inc, mc68hc705k1 Datasheet - Page 34

• Manufacturer Part Number: mc68hc705k1
• Description: Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

Central Processor Unit (CPU)
3.3.3 Stack Pointer
Technical Data
Reset:
Read:
Write:
Bit
15
0
0
= Unimplemented
14
0
0
13
0
0
The stack pointer (SP) shown in
contains the address of the next free location on the stack. During a
reset or after the reset stack pointer (RSP) instruction, the stack pointer
initializes to $00FF. The address in the stack pointer decrements as data
is pushed onto the stack and increments as data is pulled from the stack.
The 11 most significant bits of the stack pointer are fixed permanently at
00000000111, so the stack pointer produces addresses from $00E0 to
$00FF. If subroutines and interrupts use more than 32 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.
12
0
0
Freescale Semiconductor, Inc.
For More Information On This Product,
11
Figure 3-4. Stack Pointer (SP)
0
0
Central Processor Unit (CPU)
Go to: www.freescale.com
10
0
0
9
0
0
8
0
0
7
1
1
Figure 3-4
6
1
1
5
1
1
is a 16-bit register that
4
1
MC68HC705K1 — Rev. 2.0
3
1
2
1
1
1
Bit
0
1