3.2.1. Sequencer State Machine
The Ethernet IP cores for Intel® Stratix® 10 devices implement an internal state machine called Sequencer State Machine (SSM) that represents the Ethernet IP link bring-up. At any point of time, the device should be in one of SSM states.
SSM State | Description |
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SSM_ENABLE | The first state used for Sequencer State Machine (SSM) initialization. This should be the first state of device after a power cycle or a reset. If Auto Negotiation (AN) and Link Training (LT) are enabled, the local device moves to the SSM_RC_AN state after this state is completes. |
SSM_RC_AN | Indicates the reconfiguration of PHY for Auto Negotiation operation. |
SSM_AN_ABL | After the completion of SSM_RC_AN state, the local device goes into the SSM_AN_ABL state. In this state, the transmitter of the local device is disabled (i.e., no transitions) so that the Ethernet IP link goes down and the Ethernet IP link partner also goes back to Auto Negotiation. Even without any Ethernet IP link partners connected, the local device should complete this state and move to the next state i.e., SSM_AN_CHK. The local device spends an approximate time of 60 to 75 milliseconds (ms) in this state. At the end of this state, the local device starts sending AN Base Page to the remote device. |
SSM_AN_CHK | Once the local device starts sending AN base page, it moves to the state SSM_AN_CHK. The rest of the AN happens in this state. The following are major AN events that happen in this state:
Various events during AN are further categorized into a separate state machine called AN Arbiter State Machine. Refer to Auto Neg Tab for more details. |
SSM_RC_LT | Indicates the reconfiguration of PHY for LT operation. |
SSM_LT_CHK | After completion of SSM_RC_LT, device goes into SSM_LT_CHK state. This state includes the LT packet communication between the two devices, local and remote. At the end of this state, both devices should have completed LT and acknowledge each other upon completion. |
SSM_RC_10G 4 SSM_RC_DAT 5 |
Indicates that the reconfiguration of PHY for:
|
SSM_10G_CHK 4 SSM_LNK_CHK 5 |
After the completion of the SSM_RC_10G/SSM_RC_DAT state, the local device goes into the SSM_10G_CHK/SSM_LNK_CHK state. In this state, the local device tries to achieve lock on the received Ethernet packets. The following status signals shows the lock status:
The local device will move to the next state called SSM_LNK_RDY when the lock conditions are met. The local device can only remain in this state if the total time, starting from SSM_RC_LT, does not exceed 500 ms. If the total time exceeds 500 ms and the lock conditions are still not met, the local device goes back to SSM_ENABLE state and redo the AN and LT. |
SSM_LNK_RDY | Indicates that the local device has successfully locked on to the received Ethernet packets and processed them accordingly. The local device is expected to be in this state during the entire exchange of Ethernet packets unless it losses lock (rx_data_ready or rx_is_lockedtodata). If the local device losses lock, it goes to the next SSM state called SSM_LR_WAIT. |
SSM_LR_WAIT | The Ethernet IP link goes into SSM_LR_WAIT state if any of the following lock status signals goes low during SSM_LNK_RDY state:
For example, the local device wait for maximum of 1000 clock cycles to check if the lock conditions are met. If lock conditions are not met within 1000 clock cycles, the link goes back into SSM_ENABLE state. If the lock conditions are met any time before the 1000 clock cycles, the link goes back to SSM_LINK_RDY state. |