Process data (functions and oversampling)

1. Functions

• Input function: each channel of the terminal samples its input (RS or 5 V) with the set oversampling factor n (i.e. n times faster than the EtherCAT cycle time) and delivers it as bit data stream in the process image e.g. 0011001001001... via EtherCAT to the controller/PLC. The bits are combined to bytes for handling reasons.
• Output function: each channel of the terminal expects a bit data stream e.g. 01001000101... from the controller/PLC and outputs it via its output (RS or 5 V) after the set oversampling factor n (i.e. n times faster than the EtherCAT cycle time).

2. The oversampling and thus the extent of process data must be set with the TwinCAT DC dialog (see also chapter Make oversampling setting).

Fig.186: Settings "DC/Oversampling" tab

Rules:

- The oversampling factor must be the same for input and output (if both are used)
- The oversampling factor must be the same for channel 1 and 2 (if both are used)
- The resulting sampling time from EtherCAT cycle time and oversampling factor must correspond to the following formula: 100 ns + n * 20 ns ; the sampling times from the minimum are therefore 100 ns, 120 ns, 140 ns ...

For easy linking of the individual PDO variables, it is recommended to activate the Show Sub items function, then the PDOs are "expanded" and can be linked individually:

Fig.187: Show sub items" button

Fig.188: PDO tree

3. Manual PDO configuration

An individual PDO configuration, e.g. operation with input channels only or with channel 1 only, can be set manually via the PDO Assignment dialog:

Fig.189: "Process data" tab, PDO assignment

Procedure as follows:

• set the desired oversampling factor in the DC/Oversampling dialog, all PDOs are then activated
• in the SyncManager dialog, deselect the unwanted PDOs:

0,1: Mailbox, no change possible
2: Outputs channel 1
3: Inputs channel 1
4: Outputs channel 2
5: Inputs channel 1
6: empty, not to be used
7: Timestamp channel 1+2