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Glossary-5
GLOSSARY
nonvolatile memory Read-only memory that retains its contents when
power is removed. Many MCS
®
96 microcontrollers
are available with either masked ROM, EPROM, or
OTPROM. Consult the Automotive Products or
Embedded Microcontrollers databook to determine
which type of memory is available for a specific
device.
npn transistor A transistor consisting of one part p-type material and
two parts n-type material.
p-channel FET A field-effect transistor with a p-type conducting
path.
p-type material Semiconductor material with introduced impurities
(doping) causing it to have an excess of positively
charged carriers.
PC Program counter.
phase-locked loop A component of the clock generation circuitry. The
phase-locked loop (PLL) and the two input pins
(PLLEN1 and PLLEN2) combine to enable the device
to attain its maximum operating frequency with an
external clock whose frequency is either equal to,
one-half, or one-fourth that maximum frequency or
with an external oscillator whose frequency is either
one-half or one-fourth that maximum frequency.
PIC Programmable interrupt controller. The module
responsible for handling interrupts that are to be
serviced by interrupt service routines that you
provide. Also called simply the interrupt controller.
PLL See phase-locked loop.
prioritized interrupt Any maskable interrupt or nonmaskable NMI. Two of
the nonmaskable interrupts (unimplemented opcode
and software trap) are not prioritized; they vector
directly to the interrupt service routine when
executed.
program memory A partition of memory where instructions can be
stored for fetching and execution.
protected instruction An instruction that prevents an interrupt from being
acknowledged until after the next instruction
executes. The protected instructions are DI, EI, DPTS,
EPTS, POPA, POPF, PUSHA, and PUSHF.