EJ9400 - Power supply plug-in module for E-bus, 2.5 A

General notes for commissioning of the EtherCAT slave

This summary briefly deals with a number of aspects of EtherCAT Slave operation under TwinCAT. More detailed information on this may be found in the corresponding sections of, for instance, the EtherCAT System Documentation.

 

Diagnosis in real time: WorkingCounter, EtherCAT State and Status

Generally speaking an EtherCAT Slave provides a variety of diagnostic information that can be used by the controlling task.

This diagnostic information relates to differing levels of communication. It therefore has a variety of sources, and is also updated at various times.

Any application that relies on I/O data from a fieldbus being correct and up to date must make diagnostic access to the corresponding underlying layers. EtherCAT and the TwinCAT System Manager offer comprehensive diagnostic elements of this kind. Those diagnostic elements that are helpful to the controlling task for diagnosis that is accurate for the current cycle when in operation (not during commissioning) are discussed below.

 
Selection of the diagnostic information of an EtherCAT Slave

In general, an EtherCAT Slave offers

communication diagnosis typical for a slave (diagnosis of successful participation in the exchange of process data, and correct operating mode)
This diagnosis is the same for all slaves.

as well as
function diagnosis typical for a channel (device-dependent)
See the corresponding device documentation

The colors in Fig. “Selection of the diagnostic information of an EtherCAT Slave” also correspond to the variable colors in the System Manager, see Fig. “Basic EtherCAT Slave Diagnosis in the PLC”.

Colour
Meaning
yellow
Input variables from the Slave to the EtherCAT Master, updated in every cycle
red
Output variables from the Slave to the EtherCAT Master, updated in every cycle
green
Information variables for the EtherCAT Master that are updated acyclically. This means that it is possible that in any particular cycle they do not represent the latest possible status. It is therefore useful to read such variables through ADS.

Fig. “Basic EtherCAT Slave Diagnosis in the PLC” shows an example of an implementation of basic EtherCAT Slave Diagnosis. A Beckhoff EL3102 (2-channel analogue input terminal) is used here, as it offers both the communication diagnosis typical of a slave and the functional diagnosis that is specific to a channel. Structures are created as input variables in the PLC, each corresponding to the process image.

 
Basic EtherCAT Slave Diagnosis in the PLC
 
 

The following aspects are covered here:

Code
Function
Implementation
Application/evaluation
A
The EtherCAT Master's diagnostic information
updated acyclically (yellow) or provided acyclically (green).
 
At least the DevState is to be evaluated for the most recent cycle in the PLC.
The EtherCAT Master's diagnostic information offers many more possibilities than are treated in the EtherCAT System Documentation. A few keywords:
CoE in the Master for communication with/through the Slaves
Functions from TcEtherCAT.lib
Perform an OnlineScan
B
In the example chosen (EL3102) the EL3102 comprises two analogue input channels that transmit a single function status for the most recent cycle.
Status
the bit significations may be found in the device documentation
other devices may supply more information, or none that is typical of a slave
In order for the higher-level PLC task (or corresponding control applications) to be able to rely on correct data, the function status must be evaluated there. Such information is therefore provided with the process data for the most recent cycle.
C
For every EtherCAT Slave that has cyclic process data, the Master displays, using what is known as a WorkingCounter, whether the slave is participating successfully and without error in the cyclic exchange of process data. This important, elementary information is therefore provided for the most recent cycle in the System Manager
1.
at the EtherCAT Slave, and, with identical contents
2.
as a collective variable at the EtherCAT Master (see Point A)
for linking.
WcState (Working Counter)
0: valid real-time communication in the last cycle
1: invalid real-time communication
This may possibly have effects on the process data of other Slaves that are located in the same SyncUnit
In order for the higher-level PLC task (or corresponding control applications) to be able to rely on correct data, the communication status of the EtherCAT Slave must be evaluated there. Such information is therefore provided with the process data for the most recent cycle.
D
Diagnostic information of the EtherCAT Master which, while it is represented at the slave for linking, is actually determined by the Master for the Slave concerned and represented there. This information cannot be characterized as real-time, because it
is only rarely/never changed, except when the system starts up
is itself determined acyclically (e.g. EtherCAT Status)
State
current Status (INIT..OP) of the Slave. The Slave must be in OP (=8) when operating normally.
AdsAddr
The ADS address is useful for communicating from the PLC/task via ADS with the EtherCAT Slave, e.g. for reading/writing to the CoE. The AMS-NetID of a slave corresponds to the AMS-NetID of the EtherCAT Master; communication with the individual Slave is possible via the port (= EtherCAT address).
Information variables for the EtherCAT Master that are updated acyclically. This means that it is possible that in any particular cycle they do not represent the latest possible status. It is therefore possible to read such variables through ADS.
 
Note
Diagnostic information
It is strongly recommended that the diagnostic information made available is evaluated so that the application can react accordingly.
 
 

CoE Parameter Directory

The CoE parameter directory (CanOpen-over-EtherCAT) is used to manage the set values for the slave concerned. Changes may, in some circumstances, have to be made here when commissioning a relatively complex EtherCAT Slave. It can be accessed through the TwinCAT System Manager, see Fig. “EL3102, CoE directory”:

 
EL3102, CoE directory
EtherCAT System Documentation
The comprehensive description in the EtherCAT System Documentation (EtherCAT Basics --> CoE Interface) must be observed!

A few brief extracts:

Whether changes in the online directory are saved locally in the slave depends on the device. EL terminals (except the EL66xx) are able to save in this way.
The user must manage the changes to the StartUp list.
 
 

Commissioning aid in the TwinCAT System Manager

Commissioning interfaces are being introduced as part of an ongoing process for EL/EP EtherCAT devices. These are available in TwinCAT System Managers from TwinCAT 2.11R2 and above. They are integrated into the System Manager through appropriately extended ESI configuration files.

 
Example of commissioning aid for a EL3204

This commissioning process simultaneously manages

CoE Parameter Directory
DC/FreeRun mode
the available process data records (PDO)

Although the "Process Data", "DC", "Startup" and "CoE-Online" that used to be necessary for this are still displayed, it is recommended that, if the commissioning aid is used, the automatically generated settings are not changed by it.

The commissioning tool does not cover every possible application of an EL/EP device. If the available setting options are not adequate, the user can make the DC, PDO and CoE settings manually, as in the past.

 
 

EtherCAT State: automatic default behaviour of the TwinCAT System Manager and manual operation

After the operating power is switched on, an EtherCAT Slave must go through the following statuses

INIT
PREOP
SAFEOP
OP

to ensure sound operation. The EtherCAT Master directs these statuses in accordance with the initialization routines that are defined for commissioning the device by the ES/XML and user settings (Distributed Clocks (DC), PDO, CoE). See also the section on "Principles of Communication, EtherCAT State Machine" in this connection. Depending how much configuration has to be done, and on the overall communication, booting can take up to a few seconds.

The EtherCAT Master itself must go through these routines when starting, until it has reached at least the OP target state.

The target state wanted by the user, and which is brought about automatically at start-up by TwinCAT, can be set in the System Manager. As soon as TwinCAT reaches the status RUN, the TwinCAT EtherCAT Master will approach the target states.

 
 

Standard setting

The advanced settings of the EtherCAT Master are set as standard:

EtherCAT Master: OP
Slaves: OP
This setting applies equally to all Slaves.
 
Default behaviour of the System Manager

In addition, the target state of any particular Slave can be set in the "Advanced Settings" dialogue; the standard setting is again OP.

 
Default target state in the Slave
 
 

Manual Control

There are particular reasons why it may be appropriate to control the states from the application/task/PLC. For instance:

for diagnostic reasons
to induce a controlled restart of axes
because a change in the times involved in starting is desirable

In that case it is appropriate in the PLC application to use the PLC function blocks from the TcEtherCAT.lib, which is available as standard, and to work through the states in a controlled manner using, for instance, FB_EcSetMasterState.

It is then useful to put the settings in the EtherCAT Master to INIT for master and slave.

PLC function blocks
 
 

Current consumption of the EJ modules from the E-bus

Each EtherCAT module requires a certain current from the E-bus (see technical data: “Current consumption E-bus”). The information about the current required from the E-bus supply is available for each module online and in the catalogue. The precalculated theoretical maximum E-bus current is displayed in the TwinCAT System Manager. A negative total amount in conjunction with an exclamation mark indicates that the value is too low.

 
System Manager current calculation

The E-bus system voltage is provided by Bus Couplers and power supply units (see section Power supply of the EtherCAT plug-in modules).