Multiple Segments / Segment Size

General

This register configures options for how control bytes are inserted within the Input MTU blocks of the data flow.

Control bytes contain the information required to reassemble the entire frame from the segments contained in the Input MTU blocks.

Segments can have a maximum length of 63 bytes. A frame that is longer than 63 bytes must be split into several segments to be transferred. The end of the entire frame is detected using information in the control byte.

Setting: Multiple Segments Within MTU Not Permitted

If the segment ends before the end of an Input MTU, the remaining bytes of the MTU are not used in this transfer cycle. The next segment, starting with a control byte, is not started until the next cycle. Furthermore, the control byte containing the frame end identifier is also received in a separate cycle without additional data.

Setting: Multiple Segments Within MTU

If the segment ends before the end of an Input MTU, the remaining bytes of the MTU are immediately filled with the start of the next segment, which starts with a control byte.

Setting: Segment Size Maximum MTU Size

The Input MTU block begins each cycle with a control byte in RxByte1 and the length information contained in it is limited to the MTU size. The cycle that contains the last data segment can be identified using the control byte.

Setting: Segment Size May Exceed MTU Size

The first Input MTU block of the segment starts with a control byte that contains the total segment length. If this length is longer than the MTU size, then data only, without control bytes, are transferred in the following cycles until the total segment length has been reached. A new control byte is then inserted in the Input MTU for the next segment, depending on the multiple segment setting.

This setting only refers to the receiving direction of the module. In the sending direction (to the module), the application controls the behavior using control bytes. The module supports all options.