103BCommunication
10.3 PROFIBUS
S7-1200 Programmable controller
442
System Manual, 11/2011, A5E02486680-05
10.2.10
Diagnostic events for distributed I/O
Note
With a PROFINET IO system, after a download or power cycle, the CPU will go to RUN
mode unless the hardware compatibility is set to allow acceptable substitute modules
(Page 114) and one or more modules is missing or is not an acceptable substitute for the
configured module.
As shown in the following table, the CPU supports diagnostics that can be configured for the
components of the distributed I/O system. Each of these errors generates a log entry in the
diagnostic buffer.
Table 10- 34 Handling of diagnostic events for PROFINET and PROFIBUS
Type of error
Diagnostic information for
the station?
Entry in the diagnostic
buffer?
CPU operating mode
Diagnostic error
Yes
Yes
Stays in RUN mode
Rack or station failure
Yes
Yes
Stays in RUN mode
I/O access error
1
No
Yes
Stays in RUN mode
Peripheral access error
2
No
Yes
Stays in RUN mode
Pull / plug event
Yes
Yes
Stays in RUN mode
1
I/O access error example cause: A module that has been removed.
2
Peripheral access error example cause: Acyclic communication to a submodule that is not communicating.
Use the GET_DIAG instruction (Page 285) for each station to obtain the diagnostic
information. This will allow you to programmatically handle the errors encountered on the
device and if desired take the CPU to STOP mode. This method requires you to specify the
hardware device from which to read the status information.
The GET_DIAG instruction uses the "L address" (LADDR) of the station to obtain the health
of the entire station. This L Address can be found within the Network Configuration view and
by selecting the entire station rack (entire gray area), the L Address is shown in the
Properties Tab of the station. You can find the LADDR for each individual module either in
the properties for the module (in the device configuration) or in the default tag table for the
CPU.
10.3
PROFIBUS
A PROFIBUS system uses a bus master to poll slave devices distributed in a multi-drop
fashion on an RS485 serial bus. A PROFIBUS slave is any peripheral device (I/O
transducer, valve, motor drive, or other measuring device) which processes information and
sends its output to the master. The slave forms a passive station on the network since it
does not have bus access rights, and can only acknowledge received messages, or send
response messages to the master upon request. All PROFIBUS slaves have the same
priority, and all network communication originates from the master.