mc68hc05p18a Freescale Semiconductor, Inc, mc68hc05p18a Datasheet - Page 35

• Manufacturer Part Number: mc68hc05p18a
• Description: Mc68hc05p18a Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

3.3.1 Accumulator
3.3.2 Index Register
3.3.3 Stack Pointer
MC68HC05P18A
The accumulator (A) is a general-purpose 8-bit register. The CPU uses
the accumulator to hold operands and results of arithmetic and non-
arithmetic operations.
In the indexed addressing modes, the CPU uses the byte in the index
register (X) 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 (SP) 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.
Reset:
Reset:
Read:
Read:
Write:
Write:
Freescale Semiconductor, Inc.
For More Information On This Product,
Bit 7
Bit 7
Central Processor Unit (CPU)
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6
6
Figure 3-3. Index Register (X)
Figure 3-2. Accumulator (A)
5
5
Unaffected by reset
Unaffected by reset
4
4
3
3
Central Processor Unit (CPU)
2
2
1
1
Technical Data
CPU Registers
Bit 0
Bit 0