Page 52 - Engineering Digital Design

1.4 GLOSSARY OF TERMS, EXPRESSIONS, AND ABBREVIATIONS 23

Parity generator: a combinational logic device that will append a logic 1 (or logic 0) to
a binary word so as to generate an even (or odd) number of 1 's (or O's).
Passive device: any device that is incapable of producing voltage or current gain and,
thus, only dissipates power.
Pass transistor switch: a MOS transistor switch that functions as a nonrestoring switch-
ing device and that does not invert a voltage signal. A transmission gate.
PCB: printed circuit board.
p-channel: a p-type conducting region in an n-type substrate.
PDF: portable document format.
PDP: power-delay product.
PE: priority encoder.
Period: the time in seconds (s) between repeating portions of a waveform; hence, the
inverse of the frequency.
Physical truth table: an I/O specification table based on a physically measurable quantity
such as voltage.
PI: prime implicant.
Pipeline: a processing scheme where each task is allocated to specific hardware (joined
in a line) and to a specific time slot.
PIPO: parallel-in/parallel-out operation mode of a register.
PISO: parallel-in/serial-out operation mode of a register.
PL A: programmable logic array.
Planar format: a two-dimensional K-map array used to minimize functions of more than
four variables.
PLD: programmable logic device.
PLS: programmable logic sequencer.
PMOS: a p-channel MOSFET.
p-n junction diode: (see Diode)
pnp: refers to a BJT having an n-type semiconductor base and a p-type semiconductor
emitter and collector.
Polarized mnemonic: a contracted signal name onto which is attached an activation level
indicator.
Port: an entry or exit element to an entity (e.g., the name given to an input signal in a
VHDL declaration).
POS: product-of-sums.
POS hazard: a static 0-hazard.
Positional weighting: a system in which the weight of a bit in a binary word is determined
by its polynomial representation.
Positive logic: the logic system in which HV corresponds to logic 1 and LV corresponds
to logic 0.
Positive pulse: a 0-1-0 pulse.
Power, P: the product of voltage, V, and current, /, given in units of watts (W).
Power-delay product (PDP): the average power dissipated by a logic device multiplied
by its propagation delay time.
PR or PRE: preset.
Present state (PS): the logic state of an FSM at a given instant.
Present state/next state (PS/NS) table: a table that is produced from the next state
K-maps and that is used to construct a fully documented state diagram in an FSM analysis.