Datasheet

Glossary
MC9S12DP256 — Revision 1.1
Glossary
condition code register (CCR) — An 8-bit register in the CPU 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)."
CPU — See “central processor unit (CPU).”
CPU12 — The CPU of the MC68HC12 Family.
CPU clock — Bus clock select bits BCSP and BCSS in the clock select
register (CLKSEL) determine which clock drives SYSCLK for the
main system, including the CPU and buses. When EXTALi drives
the SYSCLK, the CPU or bus clock frequency (f
o
) is equal to the
EXTALi frequency divided by 2.
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.
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
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