Glossary
Appendix D
D-19
Program
A set of instructions used to control a machine or process.
Program Scan Time
The time required for the processor to execute the instructions in the
program. The program scan time may vary depending on the instructions
and each instruction’s status during the scan.
Program Storage
The portion of memory reserved for saving programs, routines,
and subroutines.
Programmable Controller
A solid-state control system which has a user-programmable memory for
storage of instructions to implement specific functions such as I/O control,
logic, timing, counting, report generation, Data Highway communication,
arithmetic, data and file manipulation. A programmable controller consists
of a central processor, input/output interface, and memory. A
programmable controller is designed as an industrial control system.
Programming Plug
A user accessible connection that establishes the operating parameters of
a module.
PROM
Programmable Read Only Memory. A type of ROM that requires an
electrical operation to store data. In use, bits or words are read on demand
but not changed.
Proportional Control
See Proportional, Integral, Derivative Control.
Proportional, Integral, Derivative Control
An intelligent I/O module or ladder diagram instruction which provides
automatic closed-loop operation of multiple continuous process control
loops. For each loop, this module can perform any or all of the following
control functions:
Proportional Control causes an output signal to change as a direct ratio
of the error signal variation.
Integral Control causes an output signal to change as a function of the
error signal time duration.
Derivative Control causes an output signal to change as a function of
the rate of change of the error signal.
Protected Memory
Data and storage locations that are inhibited from being written into.
