Rockwell Automation 1764-xxxx MICROLOGIX 1500 PROGRAMMABLE CONTROLLERS - Manual (Page 165)

Publication 1764-UM001B-EN-P - April 2002
Glossary 9
reserved bit
A location reserved for internal use.
retentive data
Information (data) that is preserved through power cycles.
RS-232
An EIA standard that specifies electrical, mechanical, and functional
characteristics for serial binary communication circuits.
run mode
An executing mode during which the controller scans or executes the
logic program.
rung
A rung contains input and output instructions. During Run mode, the
inputs on a rung are evaluated to be true or false. If a path of true
logic exists, the outputs are made true (energized). If all paths are
false, the outputs are made false (de-energized).
RTU
Remote Terminal Unit
save
To save a program to a computer hard disk.
scan
The scan is made up of four elements: input scan, program scan,
output scan, and housekeeping.
scan time
The time required for the controller to complete one scan.
sinking
A term used to describe current flow between two devices. A sinking
device provides a direct path to ground.