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SRIO lens swap.

David Danon
Prodigy 100 points

Hallo.

I am currently in the routing stage of board based on the TI DSP C6678 and IDT SRIO switch CPS1848.

1. Is it possible to swap the Plus and Minus signal of the differential SRIO pairs (for example to connect TXP to RXN and TXN to RXP) ?

2. In case of 1x4 (one channel with four lens) configuration of the SRIO can I make a swap between SRIO lens (for example connect TX0 to RX2 and TX2 to RX0) ?

 

Thanks.

David

 

  • 0
    TI__Mastermind 42545 points

    Hi David,

    1. It is possible to swap the polarity of the differential pair but the swap isn't detected automatically.  Each serdes pair has a transmit and a receive configuration register.  The SRIO_SERDES_CFGRXx register includes control bit 6 called INVPAIR.  If this bit is set to 0 the receive pair will expect normal polarity and if it is set to 1 it will expect that the polarity has been swapped. In addition there are a SRIO_SERDES_CFGTXx registers that also include the bit 6 INVPAIR control bit.  This control bit will cause the transmitter to send normal polarity if set to 0 or transmit reverse polarity if set to 1.  These registers are documented in the KeyStone Architecture Serial Rapid IO (SRIO) User Guide. 

    Note that these bits are set to 0 by default for normal polarity.  If you use the SRIO bootmode you won't have the ability to set the INVPAIR bits so you would either have to control the polarity with the transmitters of the boot device or route them without the polarity swap. 

    2. SRIO does not allow lane swapping.  You must route TX0 to RX0, TX1 to RX1, TX2 to RX2 and TX3 to RX3 for a x4 configuration.

     

  • 0 in reply to Bill Taboada
    Prodigy 100 points

    Bill.

    Thank you for fast response.

     

    David