6.2. Reset Sequence - This section shows the sequencing of signals for several typical reset scenarios. - 2026-01-06

F-Tile Ethernet Hard IP User Guide
Version
25.1.1
This section shows the sequencing of signals for several typical reset scenarios.
Figure 32. Reset Sequence
The following steps describe IP core reset sequence as shown in the waveform.
  1. Drive the i_rst_n reset signal high while i_tx_rst_n and i_rx_rst_n reset signals are already deasserted.
  2. The o_rst_ack_n reset signal deasserts. This indicates that the IP core is no longer in the full reset.
    Note: This step doesn't indicate that the IP core is in fully functional state.
    Note: The o_tx_rst_ack_n and o_rx_rst_ack_n reset signals also deassert. The exact sequence and timing is not guaranteed.
  3. The IP core is fully out of reset. Assert o_tx_lanes_stable and o_rx_pcs_ready to indicate that the TX and RX datapaths are ready for use.
  4. Assert the i_tx_rst_n reset signal.
  5. The o_tx_lanes_stable signal deasserts to indicate that the TX datapath is no longer operational.
  6. The o_tx_rst_ack_n signal asserts indicating that the TX datapath is fully in reset. Then, deassert the i_tx_rst_n signal to bring the TX datapath out of the reset.
  7. Assert the i_rx_rst_n reset signal.
  8. The o_rx_pcs_ready signal deasserts to indicate that the RX datapath is no longer operational.
  9. The o_rx_rst_ack_n signal asserts indicating that the RX datapath is fully in reset. Then, deassert the i_rx_rst_n signal to bring the RX datapath out of the reset.
  10. Assert the i_rst_n reset signal.
  11. The o_tx_lanes_stable and o_rx_pcs_ready signals deassert to indicate that TX and RX datapath are no longer operational.
  12. The o_rst_ack_n signals assert to indicate the IP core is fully in reset. To bring the IP core out of the reset, deassert the i_rst_n reset signal.

System Considerations

  • During the startup state, the system does not require asserting i_rst_n, i_tx_rst_n, and i_rx_rst_n reset signals.
  • After power on, configuration, partial reconfiguration, you must assert i_reconfig_reset signal at least once to ensure the soft CSR registers contains the reset values.
  • For external custom cadence, the custom cadence signal must be toggling before tx_lanes_stable signal comes up.
  • Similarly for PCS and PCS66 interfaces, alignment marker insertion must occur at the proper interval before tx_lanes_stable comes up.
  • During the reset, hold the i_reconfig_reset signal asserted for several valid reconfiguration clock cycles to ensure the Avalon® memory-mapped interface and soft CSRs are fully reset.
  • Access to any Avalon® memory-mapped interface is available while the i_reconfig_reset signal is low.
  • The TX and RX statistics counters are cleared with CSR registers, as well as with the respective datapath resets.
  • Pulling the cable or losing CDR lock (RX down) triggers an RX datapath reset (equivalent to i_rx_rst_n).
  • Expect the initial reset acknowledgments to be asserted even without asserting the hard resets.