RadiSys EPC-5A, Справочное руководство по аппаратному и программному обеспечению

Страница: 147 / 156

Glossary
G-9
Pinout: A diagram or table describing the location and function of pins on an
electrical connector.
Plastic Quad Flat Pack (PQFP): A popular package design for integrated circuits of
high complexity.
Power On Self Test (POST): A diagnostic routine which a computer runs at power
up. Along with other testing functions, this comprehensive test initializes the
system chipset and hardware, resets registers and flags, performs ROM
checksums, and checks disk drive devices and the keyboard interface.
Program: A set of instructions a computer follows to perform specific functions
relative to user need or system requirements. In a broad sense, a program is
also referred to as a software application, which can actually contain many
related, individual programs.
Programmable Array Logic (PAL): A semiconductor programmable ROM which
accepts customized logic gate programming to produce a desired sum-of-
products output function.

R

Random Access Memory (RAM): Memory in which the actual physical location of a
memory word has no effect on how long it takes to read from or write to that
location. In other words, the access time is the same for any address in
memory. Most semiconductor memories are RAM.
Read Only Memory (ROM): A broad class of semiconductor memories designed for
applications where the ratio of read operations to write operations is very
high. Technically, a ROM can be written to (programmed) only once, and
this operation is normally performed at the factory. Thereafter, information
can be read from the memory indefinitely.
Real Mode: The operational mode of Intelx86 CPUs that uses a segmented, offset
memory addressing method. These CPUs can address 1 MB of memory using
real mode.
Real Mode Address: A memory address composed of two 16-bit values: a segment
address and an offset quantity. A real mode address is constructed by shifting
a segment address 4 bits to the left and then adding the offset value. A real
mode address is a physical address.