FD67 Profibus-DP Manual
59
7.5.1 Troubleshooting in a Profibus network
The table below shows the most current errors in a Profibus network. This list is not exhaustive. To check correct installation, there are many useful
diagnostic tools (line tester, Profibus tester, Profibus monitor) offered by different manufacturers.
Error
DP Diagnosis
LED Display
Possible cause
Solution
The unit is not supplied.
Supply the unit.
No address is set or invalid address.
Set correct address.
The set address is already used.
An explicit and unique address must be allocated to each Profibus user.
The terminal resistor between master and
unit is switched on.
When the terminal resistor is switched on in a Profibus connector, the next user is
disconnected from the Profibus. Make sure that only the terminal resistors located
at both ends of the Profibus segment are swiitched on.
Wrong termination of the Profibus segment.
Both ends of a Profibus segment must be fitted with a terminal resistor. If low
baud rates are used, the network can apparently be operated despite wrong
termination. This may cause sporadic faults in production operation.
Spur lines
Baud rates up to 1.5 MBit/s max. 6.6 m
If higher baud rates are used, spur lines are
not admissible.
If spur lines cannot be avoided, preferably use specific „active“ spur lines or
repeaters. Please note that the number of repeaters used in a segment is limited.
Refer to the relevant documentation of the repeater.
Unit not accessible or
communication error
No slave reply
Flashing BusRun LED
on bus node.
If the module is not
supplied, all the LEDs
are off.
Extension of the Profibus segment too
large.
Admissible cable length, see table below.
Use repeaters to divide large segments into several segments.
Planned modules are different from actually
installed modules.
Check that planned modules are actually present and correctly connected to the
bus node.
Parameterisation or
configuration error
Standard specific
diagnosis
Diag.PrmFault bit
or
Diag.CfgFault bit
is set.
- Flashing BusRun LED
on bus node.
- CfgF LED is red on
bus node
Error in the internal system connection
See chapter 7.5.2.
Connection to the DP
master interrupted in
operation
No slave reply
Flashing BusRun LED.
Short-circuit or interruption in the Profibus
line.
Check the Profibus line.
Check which units are still accessible to locate the error.
(Preferably use the system with lower baud rate)
♦
Table 7-16 : Troubleshooting in a Profibus network
Baud rate in kBit/s
9,6
19,2
45,45
93,75
187,5
500
1500
3000
6000
12000
Cable lengths in m
1200
1200
1200
1200
1000
400
200
100
100
100
♦
Table 7-17 : Max. admissible cable lenghts in a Profibus segment