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Explorer
Explorer
5,855 Views
Registered: ‎09-12-2011

Spartan 6 (SP605) GTP - byte does not align

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Dear Spartan 6 Transceiver Experts out there:

 

 I have generated a transceiver design using the Spartan 6 GTP Transceiver Wizard 1.11. And I am working on using its example design to send data between 2 SP605 dev boards. I am not using any protocols at the moment. 

 

The protocol template is started from scratch, target line rate is 2.5Gbps, 8b/10b encoding and the data path width is 32 which the ref clock is 125Mhz. No channel bonding, sp605 sma connectors are used for connecting 2 dev boards. 

 

As you can see from the picture that I attached, rxbyteisaligned goes high for a short amount time and goes low again. This repeats again and again. This is related to charisk going high with the same frequency, as a result rxchariscomma and rxccommadet goes high as well with the same frequency.

 

Therefore rxlossofsynch[0] is always high, showing that transceiver is always in the resync state due to a channel realignment.

 

What do you think the problem is, maybe clocking?

 

Any help is appreciated!

 

Regards, 

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gtp_doesnotalign.png
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Explorer
Explorer
7,309 Views
Registered: ‎09-12-2011

Re: Spartan 6 (SP605) GTP - byte does not align

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I have just performed the IBERT with the same settings, the link was successful, and achieved the 2.5Gbps. I performed all 4 loopback test successfully. Therefore I am assuming that there is nothing fundametally wrong with the connection.

 

I have also tried using the aurora single lane design with the transceiver wizard with the same settings rather than using "start from scratch", this time I see that rxbyteisaligned is high all the time as expected.

 

Then I compared the designs: "start from scratch" and "single lane aurora". There were some differences in terms of GTPA1_DUAL instantiations. 

 

The main one was TXDIFFCTRL1 (Driver Swing Control) and TXPREEMPHASIS1 (Transmitter Post-Cursor TX Pre-Emphasis Control) were both tied to ground in the design which started from scratch whereas the values for different in the design with aurora. When I copied these transmit port parameters, the design from scratch's rxbyteisaligned is high all the time as expected again.

 

However I still see the rxlossofsync[1:0] = 01 in Resynch mode. And never goes to "Synch_Acquired" and data looks generally correct, but there is an increasing error in a regular way. Therefore I will mark as the question "byte does not align" is solved. I will create another message for this new concern.

 

Thanks whoever read my messages so far. 

 

Regards, 

 

Regards, 

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5 Replies
Explorer
Explorer
5,834 Views
Registered: ‎09-12-2011

Re: Spartan 6 (SP605) GTP - byte does not align

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Just to make things more complicated, I see that the errorcount1 increases even though the rxdata seems to be correct - rxdata is just an increasing value, one bit at a time. 

 

I also looked at the simulation using isim, and  rxbyteisaligned goes high and stays that way. And rxcharisk and rxcommadet is correct that it goes high in a regular interval where I do notice the BC in the rxdata which is the comma plus for alignment.  

 

According to ug386.pdf, "Commas can arrive while RXBYTEISALIGNED is High. If the commas arrive aligned to boundaries, there is no change. If the commas arrive out of position, the block deasserts RXBYTEISALIGNED until the commas are aligned again. If alignment is still activated for the comma that arrives, the block automatically aligns the new comma to the closest boundary and drives RXBYTEREALIGN High for one RXUSRCLK2 cycle."

 

But in my case rxbyteisaligned does not go low after detecting another comma. It goes right after it goes high for ~2clock cycles without no apperant reason. 

 

I think the most important things for me to figure out is 

  • why rxbyteisaligned goes low in a regular interval?

which causes the loss of sync.

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Xilinx Employee
Xilinx Employee
5,823 Views
Registered: ‎01-03-2008

Re: Spartan 6 (SP605) GTP - byte does not align

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What have you defined as the MCOMMA_10B_VALUE and P_COMMA_10B_VALUE attributes?

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Explorer
Explorer
5,821 Views
Registered: ‎09-12-2011

Re: Spartan 6 (SP605) GTP - byte does not align

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MCOMMA_10B_VALUE_0                      =>     ("1010000011"),

PCOMMA_10B_VALUE_0                      =>     ("0101111100"),

COMMA_10B_ENABLE_1                      =>     ("1111111111"),

 

more attributes:

--Comma Detection and Alignment Attributes
ALIGN_COMMA_WORD_0 => (1),
COMMA_10B_ENABLE_0 => ("1111111111"),
DEC_MCOMMA_DETECT_0 => (TRUE),
DEC_PCOMMA_DETECT_0 => (TRUE),
DEC_VALID_COMMA_ONLY_0 => (FALSE),
MCOMMA_10B_VALUE_0 => ("1010000011"),
MCOMMA_DETECT_0 => (TRUE),
PCOMMA_10B_VALUE_0 => ("0101111100"),
PCOMMA_DETECT_0 => (TRUE),
RX_SLIDE_MODE_0 => ("PCS"),
ALIGN_COMMA_WORD_1 => (1),
COMMA_10B_ENABLE_1 => ("1111111111"),
DEC_MCOMMA_DETECT_1 => (TRUE),
DEC_PCOMMA_DETECT_1 => (TRUE),
DEC_VALID_COMMA_ONLY_1 => (FALSE),
MCOMMA_10B_VALUE_1 => ("1010000011"),
MCOMMA_DETECT_1 => (TRUE),
PCOMMA_10B_VALUE_1 => ("0101111100"),
PCOMMA_DETECT_1 => (TRUE),
RX_SLIDE_MODE_1 => ("PCS"),

 

Should I be aware of something?

 

Thanks for your reply, 

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Highlighted
Explorer
Explorer
7,310 Views
Registered: ‎09-12-2011

Re: Spartan 6 (SP605) GTP - byte does not align

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I have just performed the IBERT with the same settings, the link was successful, and achieved the 2.5Gbps. I performed all 4 loopback test successfully. Therefore I am assuming that there is nothing fundametally wrong with the connection.

 

I have also tried using the aurora single lane design with the transceiver wizard with the same settings rather than using "start from scratch", this time I see that rxbyteisaligned is high all the time as expected.

 

Then I compared the designs: "start from scratch" and "single lane aurora". There were some differences in terms of GTPA1_DUAL instantiations. 

 

The main one was TXDIFFCTRL1 (Driver Swing Control) and TXPREEMPHASIS1 (Transmitter Post-Cursor TX Pre-Emphasis Control) were both tied to ground in the design which started from scratch whereas the values for different in the design with aurora. When I copied these transmit port parameters, the design from scratch's rxbyteisaligned is high all the time as expected again.

 

However I still see the rxlossofsync[1:0] = 01 in Resynch mode. And never goes to "Synch_Acquired" and data looks generally correct, but there is an increasing error in a regular way. Therefore I will mark as the question "byte does not align" is solved. I will create another message for this new concern.

 

Thanks whoever read my messages so far. 

 

Regards, 

 

Regards, 

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Newbie kiziomizio
Newbie
5,577 Views
Registered: ‎08-27-2013

Re: Spartan 6 (SP605) GTP - byte does not align

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Hi,

 

Where I can find an exaple design that you were writing on in your first post ? I need to start witch GTP but It will be easier for me if I can look inside an example project.

 

BR.

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