MC908AZ32ACFUE Datasheet, PDF (314/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Glossary
break interrupt — A software interrupt caused by the appearance on the internal address bus of the
same value that is written in the break address registers.
bus — A set of wires that transfers logic signals.
bus clock — The bus clock is derived from the CGMOUT output from the CGM. The bus clock frequency,
f_op, is equal to the frequency of the oscillator output, CGMXCLK, divided by four.
byte — A set of eight bits.
C — The carry/borrow bit in the condition code register. The CPU08 sets the carry/borrow bit when an
addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation
requires a borrow. Some logical operations and data manipulation instructions also clear or set
the carry/borrow bit (as in bit test and branch instructions and shifts and rotates).
CCR — See “condition code register.”
central processor unit (CPU) — The primary functioning unit of any computer system. The CPU controls
the execution of instructions.
CGM — See “clock generator module (CGM).”
clear — To change a bit from logic 1 to logic 0; the opposite of set.
clock — A square wave signal used to synchronize events in a computer.
clock generator module (CGM) — A module in the M68HC08 Family. The CGM generates a base clock
signal from which the system clocks are derived. The CGM may include a crystal oscillator circuit
and or phase-locked loop (PLL) circuit.
comparator — A device that compares the magnitude of two inputs. A digital comparator defines the
equality or relative differences between two binary numbers.
computer operating properly module (COP) — A counter module in the M68HC08 Family that resets
the MCU if allowed to overflow.
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.
MC68HC908AZ32A Data Sheet, Rev. 2
314
Freescale Semiconductor