BEI Sensors MHK5 Absolute Hollow Shaft Encoder - Manual (Page 44)

10.3 FAQ absolute encoder Profibus
Problem
There are problems with the profibus network (bus
error, no answer from the encoder) if one of the
following profibus masters is used:
- SIEMENS S5-95U
- Master Interface SIEMENS IM 308-B
- Softing PROFIboard
- Allen Bradley 1785 PFB/B
- Mitsubishi A1SJ 71PB92D
Possible cause
The masters do not support the full diagnostic data
length (57 bytes).
Solution
If it is possible the maximum number of diagnostic
data per slave should be increased in the master.
If this is not possible the encoder can either be
used as a „class 1“ encoder (diagnostic data length
16 bytes) or one of the manufacturer-specific
versions ( 2.1 or 2.2) can be used with reduced
diagnostics (cp. 5.1.5).
Problem
If COM PROFIBUS Version 5.0 is used it is not
possible to insert the encoder into the hardware
configuration if the PLC S5-95U is used.
Cause
The S5-95U does not support the full diagnostic
data length (57 bytes). COM PROFIBUS V5.0
checks the GSD-parameter
„Max_Diag_Data_Len=57“ and prevents the
configuration of both devices together.
Solution
Use COM PROFIBUS Version 3.3, choose one of
the manufacturer-specific -versions ( 2.1 or 2.2)
and activate the reduced diagnostics.
If COM PROFIBUS V5.0 is to be used the
configuration of the encoder is only possible with a
modified GSD file (slave key
„Max_Diag_Data_Len“ has to be changed).
Problem
PLC and master are switched on, bus is active, but
there is no answer from the encoder.
Possible solutions
First of all the state of LEDs in the connection cap
should be checked (cp. section 6.3). Possibly this
can give hints to the cause of the problem.
Both LEDs dark: Check power supply!
Both LEDs bright:
Encoder is ready but receives no configuration or
parameter telegrams. Check the address setting in
the connection cap. Check the connection of the
bus lines (BUS IN / BUS OUT). Check the
hardware configuration in your software tool.
Red LED bright, green LED flashing:
Parameter error! Check parameters, e.g. the rules
for setting the total measuring range (cp. 4.1.6)
Page 44 BEI Sensors Profibus Manual serie M Revision 03/10