Flexible Interface Examples - 1.3 English

Versal Devices Integrated 100G Multirate Ethernet MAC Subsystem Product Guide (PG314)

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1.3 English

Typical Flex I/F TX and RX transactions can be seen in the following diagrams. In this example, data transfer into the Flex I/F port is active on Client 0. The user logic drives data (tx_flex_data1 and tx_flex_data2) into the interface while asserting tx_flex_ena_0.

Note the relationship between the per-port tx_flex_stall_<N> signal and tx_flex_ena_<N>. The stall signal is output to backpressure the transfers into the Flex I/F. The interface requires that you suspend transfers (tx_flex_enain == 0) exactly three cycles after the tx_flex_stall_<N> is asserted to 1.

The user logic is responsible for inserting alignment markers. When an alignment marker is inserted, the user logic must assert tx_flex_alignmarker<N> to indicate that the data includes an AM. This prevents the scrambler from scrambling the alignment markers.
Figure 1. TX Flex Interface
In the receive direction, the Flex I/F outputs data at the configured port rate. Valid data is indicated by the per-port signal rx_flex_ena_<N>. When rx_flex_ena_<N> is deasserted, the data is invalid. Note that there is no backpressure from the user logic back to the Flex I/F port. The user logic should be able to keep up with the selected data rate.
Figure 2. RX Flex Interface