Rockwell Automation 1797-IRT8 FLEX Ex Thermocouple/RTD/mV Input Module User Manual - Manual (Page 41)

Publication 1797-6.5.2 - February 2001
Input, Status, Output and Configuration Files for the Thermocouple/RTD/mV Module on the ControlNet Network 4-3
Scheduled Data-Transfer
Scheduled data transfer:
•
is continuous.
•
is asynchronous to the controller program scan.
•
occurs at the actual rate displayed in the Actual Packet Interval
field on the programming software ControlNet I/O mapping
(monitor) screen
Unscheduled Data-Transfer
Unscheduled operations include:
•
unscheduled non-discrete I/O data transfers–through ControlNet
I/O Transfer (CIO) instructions
•
peer-to-peer messaging–through message (MSG) instructions
•
messaging from programming devices
Unscheduled messaging on a ControlNet network is
non-deterministic. Your application and your configuration–number of
nodes, application program, NUT, amount of scheduled bandwidth
used, etc.–determine how much time there is for unscheduled
messaging.
Module I/O Mapping
The I/O map for a module is divided into read words and write
words. Read words consist of input and status words, and write
words consist of output and configuration words. The number of
read words or write words can be 0 or more. The length of each I/O
module’s read words and write words vary in size depending on
module complexity. Each I/O module will support at least 1 input
word or 1 output word. Status and configuration are optional,
depending on the module.