6–2
Input, Output and Configuration Files for Analog Modules when used with ControlNet
Publication 1794-6.5.16 – September 1998
Scheduled Data-Transfer
Scheduled data transfer:
•
is continuous
•
is asynchronous to the ladder-logic 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.
For example, a 16 point discrete input module will have up to 2 read
words and 1 write word.
Module Image
Inputs
Delay
Time
Input Size
Configuration Size
1 or 2 Words
0 or 1 Word
ControlNet Image
Not used
16-point Discrete Input Module
Delay
Time
Not used
Check the I/O map for each module for the exact mapping.