M68ICS08GR datasheet(397/408 Pages) FREESCALE

397 / 408 page

Glossary

MC68HC908GR8 — Rev 4.0

Technical Data

MOTOROLA

Glossary

397

condition code register (CCR) — An 8-bit register in the CPU08 that contains the interrupt

mask bit and five bits that indicate the results of the instruction just executed.

control bit — One bit of a register manipulated by software to control the operation of the

module.

control unit — One of two major units of the CPU. The control unit contains logic functions that

synchronize the machine and direct various operations. The control unit decodes

instructions and generates the internal control signals that perform the requested

operations. The outputs of the control unit drive the execution unit, which contains the

arithmetic logic unit (ALU), CPU registers, and bus interface.

COP — See "computer operating properly module (COP)."

counter clock — The input clock to the TIM counter. This clock is the output of the TIM

prescaler.

CPU — See “central processor unit (CPU).”

CPU08 — The central processor unit of the M68HC08 Family.

CPU clock — The CPU clock is derived from the CGMOUT output from the CGM. The CPU

clock frequency is equal to the frequency of the oscillator output, CGMXCLK, divided by

four.

CPU cycles — A CPU cycle is one period of the internal bus clock, normally derived by dividing

a crystal oscillator source by two or more so the high and low times will be equal. The

length of time required to execute an instruction is measured in CPU clock cycles.

CPU registers — Memory locations that are wired directly into the CPU logic instead of being

part of the addressable memory map. The CPU always has direct access to the

information in these registers. The CPU registers in an M68HC08 are:

•

A (8-bit accumulator)

•

H:X (16-bit index register)

•

SP (16-bit stack pointer)

•

PC (16-bit program counter)

•

CCR (condition code register containing the V, H, I, N, Z, and C

bits)

CSIC — customer-specified integrated circuit

cycle time — The period of the operating frequency: t

CYC =1/fOP.

decimal number system — Base 10 numbering system that uses the digits zero through nine.

Freescale Semiconductor, Inc.

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