Rockwell Automation 1747-SCNR ControlNet Scanner Module Reference Manual - Manual (Page 25)

Publication 1747-RM623D-EN-P - June 2006
Prepare to Use the ControlNet Scanner 2-5
The ControlNet system places your scheduled transfers in the first part
of each network update interval (NUI). Time is automatically reserved
for network maintenance, and unscheduled transfers are performed
during the remainder of the interval.
Unscheduled messaging on a ControlNet network is
non-deterministic.Your application and your configuration (for
example, number of nodes, application program, NUT) determine
how much time there is for unscheduled messaging.
Understand 1747-SCNR
Mapping The 1747-SCNR scanner and the SLC processor exchange the
following information through the backplane:
• Input data
• Output data
• Status data
• Command data
• CIP messages
The 1747-SCNR mapping is described in the following. Bit field
descriptions follow each table.
Discrete Input File
IMPORTANT
The ControlNet network reserves time for at least one
unscheduled transfer per NUI.
Word
Offsets Word
Size ControlNet
Transfer Mode Contents Description
0 1 N/A Module Status (see
the next section,
“Module Status”) Bit field reporting general
status information.
1-31 31 Scheduled ControlNet Input
Data You can map up to 31 words of
input data using RSNetWorx
for ControlNet software.