MC908AZ60ACFUER Datasheet, PDF (410/414 Pages) Freescale Semiconductor, Inc – To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to:

Glossary
parity — An error-checking scheme that counts the number of logic 1s in each byte transmitted. In a
system that uses odd parity, every byte is expected to have an odd number of logic 1s. In an even
parity system, every byte should have an even number of logic 1s. In the transmitter, a parity
generator appends an extra bit to each byte to make the number of logic 1s odd for odd parity or even
for even parity. A parity checker in the receiver counts the number of logic 1s in each byte. The parity
checker generates an error signal if it finds a byte with an incorrect number of logic 1s.
PC — See “program counter (PC).”
peripheral — A circuit not under direct CPU control.
phase-locked loop (PLL) — A oscillator circuit in which the frequency of the oscillator is synchronized
to a reference signal.
PLL — See "phase-locked loop (PLL)."
pointer — 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 — The two opposite logic levels, logic 1 and logic 0, which correspond to two different voltage
levels, V_DD and V_SS.
polling — Periodically reading a status bit to monitor the condition of a peripheral device.
port — A set of wires for communicating with off-chip devices.
prescaler — 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 — A set of computer instructions that cause a computer to perform a desired operation or
operations.
program counter (PC) — 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 — An instruction that copies into the accumulator the contents of a stack RAM location. The stack
RAM address is in the stack pointer.
pullup — A transistor in the output of a logic gate that connects the output to the logic 1 voltage of the
power supply.
pulse-width — The amount of time a signal is on as opposed to being in its off state.
pulse-width modulation (PWM) — Controlled variation (modulation) of the pulse width of a signal with
a constant frequency.
push — An instruction that copies the contents of the accumulator to the stack RAM. The stack RAM
address is in the stack pointer.
PWM period — The time required for one complete cycle of a PWM waveform.
RAM — 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 — A circuit consisting of capacitors and resistors having a defined time constant.
read — To copy the contents of a memory location to the accumulator.
register — A circuit that stores a group of bits.
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
410
Freescale Semiconductor