mc68hc05x4dw Freescale Semiconductor, Inc, mc68hc05x4dw Datasheet - Page 29

• Manufacturer Part Number: mc68hc05x4dw
• Description: Xc68hc705x4 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Index Register
Stack Pointer
3-cpu
Reset
Reset:
Reset:
Bit 15 14
0
0
In the indexed addressing modes, the CPU uses the byte in the index
register to determine the conditional address of the operand.
The 8-bit index register can also serve 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 or after the reset stack pointer
(RSP) instruction, the stack pointer is preset 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 ten most significant bits of the stack pointer are permanently fixed
at 000000011, 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.
Bit 7
Bit 7
Freescale Semiconductor, Inc.
0
0
For More Information On This Product,
13
0
0
6
6
Go to: www.freescale.com
12
0
0
11
Figure 3. Index Register
0
0
Figure 4. Stack Pointer
Figure 2. Accumulator
5
5
CPU
10
0
0
9
0
0
Unaffected by reset
Unaffected by reset
4
4
8
0
0
7
1
1
3
3
6
1
1
5
1
2
2
1
4
MC68HC05X4 Rev 1.0
3
1
1
1
CPU Registers
1
2
1
1
Bit 0
Bit 0
CPU
Bit 0
1