MC68HC705P6A Datasheet, PDF (96/130 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Central Processor Unit (CPU) Core
7 6 5 432 1 0
ACCUMULATOR
A
INDEX REGISTER
X
15 14 13 12 11 10 9 8
0000000011
STACK POINTER
SP
PROGRAM COUNTER
PC
CONDITION CODE REGISTER
1 1 1H I NZC
CC
HALF-CARRY BIT (FROM BIT 3)
INTERRUPT MASK
NEGATIVE BIT
ZERO BIT
CARRY BIT
Figure 12-1. MC68HC05 Programming Model
12.3.1 Accumulator
The accumulator is a general-purpose 8-bit register as shown in Figure
12-1. The CPU uses the accumulator to hold operands and results of
arithmetic calculations or non-arithmetic operations. The accumulator is
unaffected by a reset of the device.
12.3.2 Index Register
The index register shown in Figure 12-1 is an 8-bit register that can
perform two functions:
• Indexed addressing
• Temporary storage
In indexed addressing with no offset, the index register contains the low
byte of the operand address, and the high byte is assumed to be $00. In
indexed addressing with an 8-bit offset, the CPU finds the operand
address by adding the index register contents to an 8-bit immediate
value. In indexed addressing with a 16-bit offset, the CPU finds the
Advance Information
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Central Processor Unit (CPU) Core
MC68HC705P6A — Rev. 2.0
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