Process data

The EL31xx terminals offer two different process data per analog channel for transmission: the analog value Value (16 bit) and status information (16 bit). As with individual channels, the transmission of individual status information can be deactivated in the ProcessData tab; these changes are effective after activation and an EtherCAT restart or reload.
There is a choice of two types of process data in the EL31xx:

• Standard: standard setting, Value (16 bit) and status information (8 or 16 bit) are transmitted per channel
• Compact: only the Value (16 bit) is transmitted per channel

The settings are described below, taking the EL3102 (two channels, ±10 V) as an example. The data apply to TwinCAT 2.11 from build 1544 onward and XML revision from EL31xx-0000-0016 onward.

Interpretation of value and status variable

The plain text display of the bit meanings of the status word is particularly helpful not only in commissioning but also for linking to the PLC program.
By right-clicking on the status variable in the configuration tree (A), the structure can be opened for linking (B).

In order to be able to read the bit meanings in plain text in the online display (C), the button

can be used to show all subvariables, including the structure content of the status word, see Fig. Display subvariables of the EL3102-0000-0016 from TwinCAT 2.11 build 1544

Control/status word

Status word

The status word (SW) is located in the input process image, and is transmitted from terminal to the controller.

Legend

*) from rev. EL31xx-0000-0016

Control word

The EL31xx have no control word

Changeover of process data sets

The process data to be transmitted (PDO, ProcessDataObjects) can be selected by the user

• completely for all channels via the selection dialog “Predefined PDO Assignment” (all TwinCAT versions)
• selective for individual PDOs, taking into account the excluded elements.

“Predefined PDO Assignment” selection dialog (from TwinCAT 2.11 build 1544 onwards)

Defined PDO sets can be preselected if they exist in the XML description.

All channels of the EL31x2 are simultaneously set to legacy, legacy compact, standard or compact process image.

Selective PDO selection

All TwinCAT versions support the selective selection of individual PDOs, as defined in the XML description.
Exclusion criteria prevent irregular combinations.

Explanatory notes regarding Selective PDO selection: In the “Process Data” tab, it can be seen under (A) that this EL3102 offers several different PDOs for the transmission, and in fact for each channel

• "Legacy" from CoE index 0x1A00/0x1A01: status word and measured value for channel, 3 bytes
• "Legacy compact" from CoE index 0x1A10: only measured value for 2 channels, 4 bytes
• "AI standard" from CoE index 0x1A02/0x1A04: measured value for channel and status, 4 bytes
• "AI Compact" under CoE index 0x1A03/0x1A05: only measured value for channel, 2 bytes

Legacy PDO Assignment The legacy PDO Assignment is a compatibility mode for previous 2-channel 16-bit input terminals (EL31x2) and should not be used for new configurations. This mode ensures complication-free replacement of older EL31x2 models with new ones. See also the following chapter.

By selecting the necessary Input SyncManager in (B), the PDO assignment under (C) can be carried out manually. The process data can then be linked in the TwinCAT tree (D).

Note about the 1-byte status of earlier EtherCAT terminals

Previous analog input terminals from Beckhoff (e.g. EL31x2) had a status byte instead of the status word that is now implemented and therefore a 3-byte interface. 8 additional bits now offer extended diagnostic options, wherein the default process image of the EL31xx now encompasses 4 bytes, status word and value word. The bit meanings of the LowByte are retained; Limit1 and Limit2 as 2-bit types are shown in the case of the EL31xx.

If the 3-byte interface for linking to the analogue input channel is implemented in existing PLC projects, the TwinCAT System Manager nevertheless offers the possibility to link the EL31xx with a 4-byte interface.

To do this, open the link dialog as usual by double-clicking on the variable and activate the AllTypes checkbox. As a result, variables with differing sizes are also offered for linking. Select the corresponding 1-byte input variable for your application. The 8 bit coverage is confirmed in the following SizeMismatch dialog, Fig. Element-orientated process image under TwinCAT 2.10.

Note about TwinCAT 2.10

The structured representation of EL31xx from revision EL31xx-0000-0016, as shown in Fig. Selective PDO selection is due to a corresponding interpretation of the variable names. This function does not exist in TwinCAT 2.10 yet, which is why only element-wise linking is possible there.

Password protection for user data

Several user data is protected for unrequested or mistaken write access by a password to be entered within CoE 0xF009:

• CoE write access by the user, PLC or start up entries in Single- or CompleteAccess access
• Overwriting the values by RestoreDefaultParameter access to 0x80n0 (and accordingly 0x80nD, if present)

The password protection is provided for following user data

Application of CoE 0xF009

• Insertion of 0x12345678 activates the password protection → object indicates ‘1’ (switched on)
  Protected objects can no longer be changed; there is no error message by a write access!
• Insertion of 0x11223344 deactivates the password protection → object indicates ‘0’ (switched off)

Code word index 0xF008 This CoE object has simply a vendor specific task and is not dedicated for the user.

This function is available according to the table below