MC68HC705J MOTOROLA [Motorola, Inc], MC68HC705J Datasheet - Page 48

• Manufacturer Part Number: MC68HC705J
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Central Processor Unit (CPU)
3.5 CPU Registers
3.5.1 Accumulator
3.5.2 Index Register
Technical Data
48
Reset:
Reset:
Read:
Read:
Write:
Write:
The M68HC05 CPU contains five registers that control and monitor
microcontroller unit (MCU) operation:
CPU registers are not memory mapped.
The accumulator (A) is a general-purpose 8-bit register. The CPU uses
the accumulator to hold operands and results of ALU operations.
In the indexed addressing (X) modes, the CPU uses the byte in the index
register to determine the conditional address of the operand. The index
register also can serve as a temporary storage location or a counter.
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•
•
•
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Bit 7
Bit 7
Accumulator
Index register
Stack pointer
Program counter
Condition code register
Central Processor Unit (CPU)
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
MC68HC705J1A — Rev. 4.0
2
2
1
1
MOTOROLA
Bit 0
Bit 0