The module cmac_usplus_0_pkt_gen is responsible for the generation of LBUS packets. Typically the packet generator waits for the transceivers to achieve lock and for the core RX to get aligned. After this has occurred, the packet generator sends a predefined number of packets. A Finite State Machine (FSM) is used to generate the LBUS packets. A functional description of each state follows:
• STATE_TX_IDLE : By default the controller is in this state. When reset_done becomes High, it moves to the STATE_GT_LOCKED state.
• STATE_GT_LOCKED : This state sets ctl_tx_send_rfi=1 , tx_core_busy_led=1 and gt_lock_led=1 . It then moves to the STATE_WAIT_RX_ALIGNED state.
• STATE_WAIT_RX_ALIGNED : This state waits for the 100G Ethernet IP cores to indicate stat_rx_aligned =1, which means that the 100G Ethernet IP RX core is locked. After that, it moves to the STATE_PKT_TRANSFER_INIT state.
• STATE_PKT_TRANSFER_INIT : This state sets rx_aligned_led =1 and tx_core_busy_led =1. It then initializes all signals to start LBUS packet generation and moves to the STATE_LBUS_TX_ENABLE state.
• STATE_LBUS_TX_ENABLE : This state checks for the number of packets to be generated and sends LBUS packets of a predefined size. After sending all the packets, the FSM moves to the STATE_LBUS_TX_DONE state. During transmission of the packets, if tx_rdyout =0, tc_ovfout =1 or tx_unfout =1, the FSM controller moves to the STATE_LBUS_TX_HALT state.
• STATE_LBUS_TX_HALT : In this state, the controller generates the tx_fail_reg flag if tc_ovfout or tx_unfout is High. Then the FSM moves to the STATE_LBUS_TX_DONE state. If tx_rdyout becomes High, the FSM moves to the STATE_LBUS_TX_ENABLE or STATE_PTP_PKT_TRANSFER state to proceed the packet generation.
• STATE_LBUS_TX_DONE : This state resets all signals related to packet generation and sets tx_done_led =1. If 1588 1-step or Both option with FCS insertion is enabled, it moves to STATE_PTP_PKT_INIT state, otherwise it checks if TX_FLOW_CONTROL is enabled. If enabled, the FSM moves to the STATE_TX_PAUSE_INIT state, else the FSM moves to STATE_WAIT_FOR_RESTART state.
• STATE_WAIT_FOR_RESTART : In this state, all the packet generator parameters reset to the default values and reset tx_busy_led =0. The FSM moves to STATE_PKT_TRANSFER_INIT at tx_restart_rising_edge .
• STATE_PTP_PKT_INIT : Reset all the signals used for LBUS transaction. Move to STATE_PTP_PKT_READ state wait until the initialization counter is done and set the ptp_pkt_transfer flag to 1. After sending three 1588 PTP packets (Ethernet, IPV4 and IPV6), the FSM moves to the STATE_TX_PAUSE_INIT state if the TX_FLOW_CONTROL is enabled; otherwise, the FSM moves to STATE_WAIT_FOR_RESTART state.
• STATE_PTP_PKT_READ : In case of IPV4 or IPV6, increment the tx_ptp_pkt_index and move to STATE_PTP_PKT_TRANSFER state.
• STATE_TX_PTP_PKT_TRANSFER : Read the data from the ptp_pkt_gen module after sending the complete PTP packet and move to STATE_PTP_PKT_INIT state.
• STATE_TX_PAUSE_INIT : This state sets ctl_tx_pause_enable = 9'h100 and ctl_tx_pause_req = 1 and waits for the stat_tx_pause signal to be High. Then, the FSM moves to the STATE_TX_PPP_INIT state.
• STATE_TX_PPP_INIT : In this state, the controller sets ctl_tx_pause_enable = 9'h0ff and ctl_tx_pause_req[7:0] one bit at a time in decrementing order (bit 7 to bit 0). It then waits for stat_tx_pause_valid to become High and moves to the STATE_TX_PAUSE_DONE state.
• STATE_TX_PAUSE_DONE : In this state, all the pause signals are reset. The controller then moves to the STATE_WAIT_FOR_RESTART state.
If any time stat_rx_aligned = 0, then the FSM moves to STATE_TX_IDLE state.
• In the simplex TX mode of operation, because RX alignment information will not be available, the state machine waits for the user logic to input simplex_mode_rx_aligned . After the user logic asserts this input to high, packet transmission starts.
If you select
Disable FCS Insertion
tab, then the core does not insert the CRC value for the data packets. So, a
module will be instantiated inside the
module that contains the pre-calculated CRC values for the current LBUS predefined data packets of packet size 522 bytes. These CRC values will be appended at the end of each LBUS packet.
Therefore, if you change the packet size, you must change the CRC values for this new module as appropriate for the new packets and packet size.
• In case of 1588 Transparent Clock '1-step' or 'Both' option selected and if FCS insertion is disabled in the Vivado IDE, then the 1588 Transparent Clock testing is not performed in example design, because of the unpredictable PTP frame CRC values as core will modify the packet.
• If you select the 1588 '1-step' or 'Both' option in the General tab, the ptp_packet_gen module will be instantiated inside the cmac_usplus_0_packet_gen module. This module contains three 1588 PTP packets (Ethernet, IPV4 and IPV6) with or without the CRC values based on the Disable FCS Insertion or Enable FCS Insertion option in the GUI tab-1.
The state transition occurring during this process is shown in This Figure .