Datasheet

Central Processing Unit (CPU)
CPU registers
MC68HC908GR8 — Rev 4.0 Technical Data
MOTOROLA Central Processing Unit (CPU) 141
10.4.1 Accumulator (A)
The accumulator is a general-purpose 8-bit register. The CPU uses the
accumulator to hold operands and the results of arithmetic/logic
operations.
10.4.2 Index register (H:X)
The 16-bit index register allows indexed addressing of a 64K byte
memory space. H is the upper byte of the index register and X is the
lower byte. H:X is the concatenated 16-bit index register.
In the indexed addressing modes, the CPU uses the contents of the
index register to determine the conditional address of the operand.
The index register can also be used as a temporary data storage
location.
Bit 7654321Bit 0
A
Read:
Write:
Reset: Unaffected by reset
Figure 10-2. Accumulator (A)
Bit
151413121110987654321
Bit
0
H:X
Read:
Write:
Reset:00000000XXXXXXXX
X = Indeterminate
Figure 10-3. Index register (H:X)
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cale Semiconductor,
I
Freescale Semiconductor, Inc.
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