MC68HC705C9ACFN datasheet(44/157 Pages) FREESCALE

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General Release Speciﬁcation

CPU Registers

MC68HC705C9A — Rev. 2.0

Central Processing Unit

3.3.5 Condition Code Register (CCR)

The 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.

Half Carry (H)

This bit is set during ADD and ADC operations to indicate that a carry

occurred between bits 3 and 4.

Interrupt (I)

When this bit is set, the timer, SCI, SPI, 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.

Negative (N)

When set, this bit indicates that the result of the last arithmetic, logical,

or data manipulation was negative.

Zero (Z)

When set, this bit indicates that the result of the last arithmetic, logical,

or data manipulation was zero.

Carry/Borrow (C)

When set, this bit indicates that a carry or borrow out of the arithmetic

logical unit (ALU) occurred during the last arithmetic operation. This

bit is also affected during bit test and branch instructions and during

shifts and rotates.

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MC68HC705C9ACFN Datasheet(PDF) 44 Page - Freescale Semiconductor, Inc