M68HC08 datasheet(74/288 Pages) FREESCALE

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Central Processor Unit (CPU)

Data Sheet

MC68HC908BD48 — Rev. 2.1

Central Processor Unit (CPU)

Freescale Semiconductor

C — Carry/Borrow Flag

The CPU sets the carry/borrow flag when an addition operation

produces a carry out of bit 7 of the accumulator or when a subtraction

operation requires a borrow. Some instructions — such as bit test and

branch, shift, and rotate — also clear or set the carry/borrow flag.

1 = Carry out of bit 7

0 = No carry out of bit 7

6.5 Arithmetic/Logic Unit (ALU)

The ALU performs the arithmetic and logic operations defined by the

instruction set.

Refer to the CPU08 Reference Manual (Freescale document order

number CPU08RM/AD) for a description of the instructions and

addressing modes and more detail about the architecture of the CPU.

6.6 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption

standby modes.

6.6.1 Wait Mode

The WAIT instruction:

•

Clears the interrupt mask (I bit) in the condition code register,

enabling interrupts. After exit from wait mode by interrupt, the I bit

remains clear. After exit by reset, the I bit is set.

•

Disables the CPU clock

M68HC08 数据表(PDF) 74 Page - Freescale Semiconductor, Inc