Rockwell Automation 1747-SCNR ControlNet Scanner Module Reference Manual - Manual (Page 34)

Publication 1747-RM623D-EN-P - June 2006
3-2 Configure and Map Scheduled Data Exchange with RSNetWorx for ControlNet Software
Data Transfer Mapping You can use the configuration software (RSNetWorx for ControlNet
software) to select either Input or M1 files for input data and either
Output or M0 files for output data. However, it is more appropriate to
use Input and Output files for critical I/O data transfer and M1 and M0
for non-critical I/O data transfer.
Input and Output files contain 31 words each. These files are
appropriate for discrete data. If you have more than 31 words to
transfer, you have to map the remaining connections in M1 and M0
ControlNet data areas.
For input data, you can map your connections anywhere in Input and
M1 ControlNet data areas. It is not possible to overlap the mapping of
two independent input connections.
For output data, you can map your connections anywhere in Output
and M1 ControlNet data areas (refer to chapter 2 for exact memory
mapping.) The overlapping of two output connections is authorized.
Data exchanged through a single connection cannot be split between
two distinct locations. This means that a 5 word connection cannot
start at location I:29 and continue at another location in the M1 file.
Likewise, you cannot configure this connection with two first words at
address M1:e.4 and M1:e.5 and the rest between M1:10 and M1:12.
You access ControlNet data located in M1 and M0 files using the COP
(copy) instruction in your ladder program. Since the maximum data
length you can transfer with the COP instruction is 128 words, you
need two instructions to copy the whole ControlNet area and control
and status word in processor memory. If you have less than 128
words of data mapped in an M file, we recommend that you pack
them together so that you can use a single copy instruction.
When you are building your mapping, we recommend that you save
free space between device connections if the size of these
connections may increase in the future.
IMPORTANT
It is your responsibility to check that no unexpected
overlapping has been configured.
IMPORTANT
To ensure data consistency at the connection level,
be sure that, for all connections configured, data of a
same connection are copied into processor memory
using a single copy instruction.