MC912DG128ACPVE Datasheet, PDF (468/478 Pages) Freescale Semiconductor, Inc – Upward compatible with M68HC11 instruction set

Glossary
Freescale Semiconductor, Inc.
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 clock generator circuit in which a voltage controlled oscillator
produces an oscillation which 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 CPU. 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.
Technical Data
468
MC68HC912DT128A — Rev 4.0
Glossary
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA