RadiSys EPS-6315, Hardware Reference Manual, Page: 118 / 123

EPC
®
-6315 Hardware Reference
108
physical
address
The address or location in memory where data is stored before it is moved as memory
remapping occurs. The physical address is that which appears on the computer’s
address bus when the CPU requests data from a memory address. When remapping
occurs, the data can be moved to a different memory location or logical address.
pinout
A diagram or table describing the location and function of pins on an
electrical connector.
PMC
(PCI Mezzanine Card) A new standard form factor for PCI add-in modules. PMCs
mate with their respective connectors on the motherboard and are secured with
screws.
PLL
(Phase-Locked Loop) A semiconductor device which functions as an electronic
feedback control system to maintain a closely regulated output frequency from an
unregulated input frequency. The typical PLL consists of an internal phase
comparator or detector, a low pass filter, and a voltage controlled oscillator which
function together to capture and lock onto an input frequency. When locked onto
the input frequency, the PLL can maintain a stable, regulated output frequency
(within bounds) despite frequency variance at the input.
POST
(Power On Self Test) 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.
PQFP
(Plastic Quad Flat Pack) A popular package design for integrated circuits of high
complexity.
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.
PS/2
(Personal System 2) Computers designed with IBM’s proprietary bus architecture
known as Micro Channel.
PSB
Processor Side Bus.
RAM
(Random Access Memory) 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.
RAS
(Row Address Strobe) An input signal to an internal DRAM latch register specifying
the row at which to read or write data. The DRAM requires a row address and a
column address to define a memory address. Since both parts of the address are
applied at the same DRAM inputs, use of row addresses and column addresses in a
multiplexed array allows use of half as many pins to define an address location in a
DRAM device as would otherwise be required.
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.