MC68HC908MR8 Datasheet, PDF (361/372 Pages) Motorola, Inc – Microcontrollers

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 an output of the prescaler
sub-module. The frequency of the counter clock is f_TCNT, and the period is t_TCNT.
CPU — See central processor unit (CPU).
CPU08 — The central processor unit of the M68HC08 Family.
CPU cycles — A CPU clock cycle is one period of the internal bus-rate clock, f_OP, 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
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
361