Indu-Sol PB-INspektor, Manual

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PB-INspektor
®
Commissioning
Page 17
Not all diagnostics are relevant to PROFIBUS device faults. Which of them are
depends on the device type and its configuration in the PLC program, so that
this decision also has to be made on a case to case basis. In the Extended
View of the Alarms/Snapshots settings, you can set the Internal Diagnostics
and/or External Diagnostics threshold to a value greater than “1” for a specific
device only, or disable it for that device by entering “0”.
5.2.5 Troubleshooting
The best approach when looking for the cause of communication faults, such
as error frames or retransmission, is to start by ignoring the diagnostics for all
PROFIBUS devices. This is done by entering “0” for the threshold settings of
each device.
To find the cause of device faults, on the other hand, it is the diagnostics that
are relevant.
If you are uncertain how to evaluate the measurement results, you should
have your network tested by a PROFIBUS specialist. The specialist will find
and correct any existing faults, and set the appropriate threshold values for
your system.
Quality Parameters Manual
Page 18
6 Quality Parameters
6.1 Drop-outs
The PROFIBUS INspektor detects drop-outs in two different ways:
1. Detection of parameter frames
A PROFIBUS device receives a parameter frame from the bus master
when it needs to be newly added to the bus (restart) or when the de-
vice has transmitted a diagnostic frame requesting parameterization.
In all three cases, the PROFIBUS device cannot exchange user data
any longer and is thus considered dropped.
2. No reply from PROFIBUS device
PROFIBUS devices are only parameterized when they are started or
restarted (after drop-out). Even if no parameter frame occurs during
monitoring, the PROFIBUS INspektor can still determine a device
failure from the missing reply.
6.2 Diagnostics
If a fault or exception condition occurs in a PROFIBUS device, the master is
informed by one of the following three frame types:
x DH response, regular diagnostic message that occurs when an error
state has newly occurred, changed or gone away during cyclic data
exchange; e.g. if a wire of an external sensor breaks at an analog 4-
20 mA input – the INspektor interprets this frame as “External
Diagnostics”
x RS response when a service request received previously from the
master cannot be executed because of an error (in that case DP
slaves are usually no longer in cyclic data exchange); e.g. in case of
an internal fault in a remote I/O module, causing incomplete or no data
to be supplied – the INspektor interprets this frame as “Internal
Diagnostics”
x RR response in the case of a dynamic overload that prevents saving
and processing the frame received previously from the master – the
INspektor interprets this frame as “Internal Diagnostics”
The devices' responses regarding the diagnostics vary from manufacturer to
manufacturer; there is no standardization in that respect. Some devices do not
distinguish between external and internal diagnostics and only report one type.