SMP Gateway User Manual • 253
Verify the packet size.
Make sure all scanning sequences are configured.
Does the device support the scanning parameters?
Different versions of the same device sometimes react differently.
We suggest you take the following steps:
Examine the protocol layer byte exchanges, using SMP Trace and SMP Stats.
Using SMP Config, make sure you have specified the correct protocol.
Look at the SMP Config general settings:
Check the settings of the protocol instance, such as packet size.
Make sure the device or link address is correct.
Check the polling parameters.
Some devices are not able to respond to rapid polling requests because they process the
information very slowly. Other devices only allow slow communications links - 9600
baud or less. If you poll too quickly, the request will arrive before the last block of data is
read, thereby causing communications problems.
28.4 Problems with Data Validity
When all the exchanges are taking place correctly and there are no protocol errors reported in the
statistics, but some of the acquired values are erroneous or incoherent:
Using SMP Config, examine the following settings for the points that are invalid:
Data point address.
Is the address of the physical data point correct? Some devices have flexible
configuration options, so you have to compare the SMP Config values with the values
set by the device manufacturer’s software.
Conversion factors.
For physical analog data points, are the scale and offset factors correct?
Polarity.
For physical binary input points, Is the polarity set correctly?
Warning messages.
Are there any warning messages in the message pane, regarding the data points that have
erroneous values?
28.5 Problems Executing a Control Operation
When a control operation fails:
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