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
