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Participant rybol
Participant
8,386 Views
Registered: ‎01-12-2012

GTX SATA template - external data width

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Hi,

 

why in the GTX SATA template can't I choose External Data Width as 10 bits? I need to have Gen1 with 150MHz and 10bit data. May choosing 20-bit data and using only half of it have any bad consequences? The 8B10B encoder and decoder are bypassed.

 

Thanks,

Tomasz

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Explorer
Explorer
15,010 Views
Registered: ‎02-22-2010

Re: GTX SATA template - external data width

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The GTX will generate a 20b data at 75MHz and you will have to implement the width conversion in the logic.

 

  1. Bring txoutclk (75MHz) to an MMCM to generate the 150MHz clock for your fabric data path and the 75MHz for txusrclk at the GTX.
  2. In the transmit you will double the data width (not only txdata but txchardispmode, etc.) by halving the 150MHz.
  3. In the receive you will convert from rxusrclk (75MHz) to the 150MHz domain by halving the data width.

 

There is a good example, in the "transceiver" hdl module of the Ethernet 1000base-x pcs/pma Core Example design. In that case the conversion is between the 125MHz @8b used by the core, and the 62.5MHz @16b required by the GTX.

2 Replies
Highlighted
Explorer
Explorer
15,011 Views
Registered: ‎02-22-2010

Re: GTX SATA template - external data width

Jump to solution

The GTX will generate a 20b data at 75MHz and you will have to implement the width conversion in the logic.

 

  1. Bring txoutclk (75MHz) to an MMCM to generate the 150MHz clock for your fabric data path and the 75MHz for txusrclk at the GTX.
  2. In the transmit you will double the data width (not only txdata but txchardispmode, etc.) by halving the 150MHz.
  3. In the receive you will convert from rxusrclk (75MHz) to the 150MHz domain by halving the data width.

 

There is a good example, in the "transceiver" hdl module of the Ethernet 1000base-x pcs/pma Core Example design. In that case the conversion is between the 125MHz @8b used by the core, and the 62.5MHz @16b required by the GTX.

Participant rybol
Participant
8,351 Views
Registered: ‎01-12-2012

Re: GTX SATA template - external data width

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ezequielsasky,

your suggestion seems reasonable. Thanks!

 

Tomasz

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