[T10] [SPL-4] Query regarding SPL Packet Synchronization

Tim Symons tim.symons at microsemi.com
Tue Feb 21 17:32:07 PST 2017


Lana
Thank you for your enquiry. All references in my response at for SPL4r11 since this is the latest revision of the standard.

The SP_PS state machine (5.16) is different from the SP_ReSync state machine (5.17).

During Train-Rx the phy is powered on, and the link negotiation process required the SP_ReSync state machine to respond to the PACKET _SYNC_LOST messages from the SP receiver.

5.14.4.10 SP15:SAS_PHY_Ready describes the conditions after the phy initialization and link negotiation is completed. As you have correctly identified for an SP transmitter that is transmitting at 22.5Gb/s , then a Start PS message is sent to the SP_PS state machine.

The SP_PS state machine forces the SPL packet header into the correct position to form an SPL packet.
If the receiver loses the header position then the SP_PS state machine tries to recover synchronization (see 5.16).
If the SP_PS state machine fails to recover synchronization it will enter the SP_PS6:Lost3 state (see 5.16.9), which sends a Resynchronize message to the SP_ReSync state machines (see 5.17) to send Transmit PACKET_SYNC_LOST messages to the SP transmitter.

Please let me know if you need further information on this.

Regards
Tim Symons
Editor of SPL


From: t10-bounces at t10.org [mailto:t10-bounces at t10.org] On Behalf Of Lana Chan
Sent: Thursday, February 9, 2017 9:14 AM
To: t10 at t10.org
Subject: [T10] [SPL-4] Query regarding SPL Packet Synchronization

EXTERNAL EMAIL
Hello,
I have a question regarding SPL Packet Synchronization

Reference 1 - In Spl4Rev08, in Packet Mode Train Rx SNW (Speed Negotiation Window), page no. 231, it indicates

If the PHY's receiver:

a)      Achieves SPL packet synchronization within the TLT, then, after completing transmission of the current PACKET_SYNC_LOST, the PHY shall change from transmitting PACKET_SYNC_LOSTs to transmitting PACKET_SYNCs for the remainder of the Train_Rx-SNW window time (i.e., the remainder of the SNW time); or

b)      Does not achieve SPL packet synchronization within the TLT, then the phy shall continue transmitting PACKET_SYNC_LOSTs for the remainder of the MRTT (i.e., the remainder of the SNW time).

Reference 2 - In Spl4Rev08, Section - 5.14.4.10
>From the SP Phy Layer state machine, Start PS message(which starts SPL Packet Synchronization state machine) is enabled after Phy_Ready.

Question:
Which SPL packet synchronization is the specification talking about in Train-Rx SNW ?

Kind Regards
Lana
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