Rockwell Automation 1764-xxxx MICROLOGIX 1500 PROGRAMMABLE CONTROLLERS - Manual (Page 158)

Publication 1764-UM001B-EN-P - April 2002
Glossary 2
communication scan
A part of the controller’s operating cycle. Communication with devices
(such as other controllers and operator interface devices) takes place
during this period.
control program
User logic (the application) that defines the controller’s operation.
controller
A device, such as a programmable controller, used to control output
devices.
controller overhead
A portion of the operating cycle used for housekeeping purposes
(memory checks, tests, communications, etc.).
counter
A device that counts the occurrence of an event.
CPU (Central Processing Unit)
The decision-making and data storage section of a programmable
controller.
data table
The part of processor memory that contains I/O status and files where
user data (such as bit, integer, timers, and counters) is monitored,
manipulated, and changed for control purposes.
DIN rail
Manufactured according to Deutsche Industrie Normenausshus (DIN)
standards, a metal railing designed to ease installation and mounting
of your devices.
download
The transfer of program or data files to a device.
DCD
Data Carrier Detect. A signal generated by a modem that represents
traffic (activity) on a communications network.