Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 208)

Glossary
Appendix B
BĆ15
Revision
A firmware change which does not greatly affect unit or module function. In
Allen-Bradley PCs this is indicated by a slash and a letter following the series
letter (e.g., series B/C).
ROM
Acronym for Read Only memory. A ROM is a solid state digital storage
memory whose contents cannot be altered by the PC.
Routine
A sequence of PC instructions which monitors and controls a specific
application function.
Rung
A grouping of PC instructions which controls one output or storage bit. This is
represented as one section of a logic ladder diagram.
Scan Time
The time necessary to completely execute the entire PC program one time.
Scanner Module
A basic PC processor module which provides I/O data communication between
the processor and the I/o chassis. As it scans the I/O racks, the states (“1” and
“0”) of the image table bits monitor and control the states (on and off) of the I/O
module terminals.
Scrolling
A multiple rung display function which allows all displayed rungs to be moved
up or down, adding the next (or preceding) rung at the bottom (or top) of the
display. As determined by the user, the display may be changed either one rung
at a time or continuously.
Search Function
A PC programming equipment feature which allows the user to quickly display
and/or edit any instruction in the PC program.
Sequencer
A controller which operates an application through a fixed sequence of events.
(See mechanical drum programmer). In contrast, a PC functions according to
varying I/O patterns.
Serial Operation
Type of information transfer within a programmable controller whereby the bits
are handled sequentially rather than simultaneously, as they are in parallel
operation. Serial operation is slower than parallel operation for equivalent
clock rate. However, only one channel is required for serial operation.