MC68HC05P18 Datasheet, PDF (37/144 Pages) Freescale Semiconductor, Inc – Advance Information

Freescale Semiconductor, Inc.
Central Processing Unit (CPU)
CPU Registers
3.3.1 Accumulator (A)
The accumulator is a general-purpose 8-bit register used to hold
operands and results of arithmetic calculations or data manipulations.
7
0
A
3.3.2 Index Register (X)
The index register is an 8-bit register used for the indexed addressing
value to create an effective address. The index register may also be
used as a temporary storage area.
7
0
X
3.3.3 Condition Code Register (CCR)
The condition code register (CCR) is a 5-bit register in which four bits are
used to indicate the results of the instruction just executed, and the fifth
bit indicates whether interrupts are masked. These bits can be
individually tested by a program, and specific actions can be taken as a
result of their state. Each bit is explained in the following paragraphs.
CCR
H I NZC
3.3.3.1 Half Carry (H)
This bit is set during ADD and ADC operations to indicate that a carry
occurred between bits 3 and 4.
3.3.3.2 Interrupt (I)
When this bit is set, the timer and external interrupt are masked
(disabled). If an interrupt occurs while this bit is set, the interrupt is
latched and processed as soon as the interrupt bit is cleared.
MC68HC(8)05P18 — Rev. 2.0
MOTOROLA
Central Processing Unit (CPU)
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Advance Information
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