Operating modes

The EPP31xx supports three different operation modes:

• Freerun (filter on, timer interrupt)
• Synchronous (filter off, SyncManager interrupt) and
• DC (DC-Sync-Interrupt)

The module switches between the "Freerun" (filter on) and "Synchron" operation modes by activating/deactivating the filter via the index. This takes place while the module is in OP mode. The changeover may result in longer sampling times and step changes in the process data until the filters have assumed a steady state.

"DC" operation mode can only be used when the filters are switched off. Likewise, it is not possible to switch the filters on in DC mode. The DC mode is parameterized via the DC tab in the TwinCAT System Manager.

Synchron mode

In synchronous operation process data are generated frame-triggered, so that a new value is available with each PLC cycle. Synchronous mode is used automatically with the EPP31xx modules (filter off, no DC).

DC operation

In DC mode the analog sampling is triggered by DC-interrupt. As a result, the temporal jitter between two frames is no longer important and the sampling point is the same across the entire system.

The "input-based" mode shifts the sync-interrupt in such a way that the process data are ready for collection shortly before the current process data cycle.

If the frame jitter is too large, it is possible that data may be collected twice or there may be interruptions in the transmission. In that case the jitter is to be reduced through TwinCAT system measures or a slower cycle time is to be chosen.

Filter operation (FIR and IIR), index 0x80n0:06, 0x80n0:15

The EPP31xx modules incorporate a digital filter which, depending on its settings, can adopt the characteristics of a Finite Impulse Response filter (an FIR filter), or an Infinite Impulse Response filter (an IIR filter). The filter is deactivated by default. Please observe the following note regarding activation with index 0x8000:06.

Activation of the filter (index 0x8000: 06), setting of the filter properties (index 0x8000:15) The filter frequencies are set centrally for all channels of the EPP3xxx modules via index 0x8000:15 (channel 1). The corresponding indices 0x80n0:15 of the other channels have no parameterization function.