Peripheral Device
peripheral servicing
PID Unit
polling
present value
printed circuit board
Programmable Controller
Programming Console
Programming Device
PROM
PROM Writer
prompt
protocol
PV
Rack
Glossary
Devices connected to a PC System to aid in system operation. Peripheral de-
vices include printers, programming devices, external storage media, etc.
Processing signals to and from peripheral devices, including refreshing, com-
munications processing, interrupts, etc.
A Unit designed for PID control.
The process whereby a device consecutively sends signals to other devices in
the same network to pass data back and forth, e.g., as in a data link.
The current value registered in a device at any instant during its operation. Pres-
ent value is abbreviated as PV. The use of this term is generally restricted to tim-
ers and counters.
A board onto which electrical circuits are printed for mounting into a computer or
electrical device.
A computerized device that can accept inputs from external devices and gener-
ate outputs to external devices according to a program held in memory. Pro-
grammable Controllers are used to automate control of external devices. Al-
though single-unit Programmable Controllers are available, building-block Pro-
grammable Controllers are constructed from separate components. Such Pro-
grammable Controllers are formed only when enough of these separate compo-
nents are assembled to form a functional assembly, i.e., there is no one individu-
al Unit called a PC.
The simplest form of Programming Device available for a PC. Programming
Consoles are available both as hand-held models and as CPU-mounting mod-
els.
A Peripheral Device used to input a program into a PC or to alter or monitor a
program already held in the PC. There are dedicated programming devices,
such as Programming Consoles, and there are non-dedicated devices, such as
a host computer.
Programmable read-only memory; a type of ROM into which the program or
data may be written after manufacture, by a customer, but that is fixed from that
time on.
A peripheral device used to write programs and other data into a ROM for per-
manent storage and application.
A message or symbol that appears on a display to request input from the opera-
tor.
The parameters and procedures that are standardized to enable two devices to
communicate or to enable a programmer or operator to communicate with a de-
vice.
See present value.
An assembly that forms a functional unit in a Rack PC System. A Rack consists
of a Backplane and the Units mounted to it. These Units include the Power Sup-
ply, CPU, and I/O Units. Racks include CPU Racks, Expansion I/O Racks, and
I/O Racks. The CPU Rack is the Rack with the CPU mounted to it. An Expansion
I/O Rack is an additional Rack that holds extra I/O Units. An I/O Rack is used in
the C2000H Duplex System, because there is no room for any I/O Units on the
CPU Rack in this System.
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