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MC68HC08AZ32A Datasheet, PDF (306/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit | |||
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Glossary
phase-locked loop (PLL) â A oscillator circuit in which the frequency of the oscillator is synchronized
to a reference signal.
PLL â See "phase-locked loop (PLL)."
pointer â Pointer register. An index register is sometimes called a pointer register because its contents
are used in the calculation of the address of an operand, and therefore points to the operand.
polarity â The two opposite logic levels, logic 1 and logic 0, which correspond to two different voltage
levels, VDD and VSS.
polling â Periodically reading a status bit to monitor the condition of a peripheral device.
port â A set of wires for communicating with off-chip devices.
prescaler â A circuit that generates an output signal related to the input signal by a fractional scale factor
such as 1/2, 1/8, 1/10 etc.
program â A set of computer instructions that cause a computer to perform a desired operation or
operations.
program counter (PC) â A 16-bit register in the CPU08. The PC register holds the address of the next
instruction or operand that the CPU will use.
pull â An instruction that copies into the accumulator the contents of a stack RAM location. The stack
RAM address is in the stack pointer.
pullup â A transistor in the output of a logic gate that connects the output to the logic 1 voltage of the
power supply.
pulse-width â The amount of time a signal is on as opposed to being in its off state.
pulse-width modulation (PWM) â Controlled variation (modulation) of the pulse width of a signal with
a constant frequency.
push â An instruction that copies the contents of the accumulator to the stack RAM. The stack RAM
address is in the stack pointer.
PWM period â The time required for one complete cycle of a PWM waveform.
RAM â Random access memory. All RAM locations can be read or written by the CPU. The contents of
a RAM memory location remain valid until the CPU writes a different value or until power is turned off.
RC circuit â A circuit consisting of capacitors and resistors having a defined time constant.
read â To copy the contents of a memory location to the accumulator.
register â A circuit that stores a group of bits.
reserved memory location â A memory location that is used only in special factory test modes. Writing
to a reserved location has no effect. Reading a reserved location returns an unpredictable value.
reset â To force a device to a known condition.
ROM â Read-only memory. A type of memory that can be read but cannot be changed (written). The
contents of ROM must be specified before manufacturing the MCU.
SCI â See "serial communication interface module (SCI)."
serial â Pertaining to sequential transmission over a single line.
serial communications interface module (SCI) â A module in the M68HC08 Family that supports
asynchronous communication.
MC68HC08AZ32A Data Sheet, Rev. 2
306
Freescale Semiconductor
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