Other important information about autoscan – Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual User Manual
Page 112
Publication 1747-UM655B-EN-P - June 2007
112 AutoScan
Other Important Information
about AutoScan
The factory default setting for AutoScan is disabled for all products.
Make sure that input or output data memory size in the scanner is
large enough to accommodate the size required based on the number
of nodes on the network and the AutoScan I/O allocation size per
node.
TIP
Nodes 0…61 inclusive are scanned and added to the scanlist if
they are not already mapped and size exists. For maximum
capacity for slave devices the scanner node address could be
configured as node 62; node 63 could also be used but to avoid
duplicate node address issues with new devices this is not
suggested.
EXAMPLE
If the I/O allocation size per node is configured for 16 bytes and
there are 32 slave devices on the network (node addresses
1…32), AutoScan would require 16 bytes x 32 = 512 bytes (256
words) of I/O space in both the scanner's input and output
table. Assuming it is an SLC system, the maximum scanner
input data table size is 150 words for input and output. The
required space exceeds what the 1747-SDN module can
support. The user would need to adjust the I/O allocation size or
reduce the slave device count on the network to include all of
the devices in the scanlist. Devices outside of the scanner's
allowable I/O image space will be rejected and will not be
included in the scanlist.
Scanlist
Data
Allocation
(bytes)
Max Node
Data
Allocation
(bytes)
Max Node
1 61
17
16
2
61
18
15
3
61
19
15
4
61
20
14
5
59
21
13
6
49
22
12
7
41
23
12
8
36
24
11
9
32
25
11
10
29
26
10