MC908GR8CDWE Datasheet, PDF (141/408 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Freescale Semiconductor, Inc.
Central Processing Unit (CPU)
CPU registers
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.
Bit 7
Read:
A
Write:
Reset:
6
5
4
3
2
Unaffected by reset
Figure 10-2. Accumulator (A)
1
Bit 0
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.
Bit
Bit
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Read:
H:X
Write:
Reset: 0 0 0 0 0 0 0 0 X X X X X X X X
X = Indeterminate
Figure 10-3. Index register (H:X)
The index register can also be used as a temporary data storage
location.
MC68HC908GR8 — Rev 4.0
MOTOROLA
Central Processing Unit (CPU)
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Technical Data
141