DS80PCI800 EEPROM Configuration

Moving to high speed interface

Hi Christian,

Please post your original EEPROM code so I can review it.  It will be helpful to debug this issue.  Generally RATE = Float will work for all PCIe applications.

Regards,

Lee

Hi Lee,

thanks for your answer.
Find below my current EEPROM configuration:

{0x43,0x00,0x10,0x00,0x0B,0x00,0x30,0x00,0x55,0x00,0x7A,

0x00,0x00,0x04,0x07,0x00},
{0x01,0xAD,0x40,0x10,0x18,0xD4,0x01,0x01,0xAD,0x40,0x10,0x1A,0xD4,0x01,0x82,0x03},
{0x5A,0x80,0x20,0x35,0xA8,0x02,0x03,0x5A,0x80,0x20,0x35,0xA8,0x00,0x00,0x54,0x54},

{0x00,0x00,0x04,0x07,0x00,0x01,0xAD,0x40,0x10,0x18,0xD4,0x01,0x01,0xAD,0x40,0x10},
{0x1A,0xD4,0x01,0x82,0x03,0x5A,0x80,0x20,0x35,0xA8,0x02,0x03,0x5A,0x80,0x20,0x35},
{0xA8,0x00,0x00,0x54,0x54,

0x00,0x00,0x04,0x07,0x00,0x03,0xAD,0x40,0x10,0x3A,0xD4},
{0x01,0x03,0xAD,0x40,0x10,0x3A,0xD4,0x01,0x82,0x07,0x5A,0x80,0x20,0x75,0xA8,0x02},
{0x07,0x5A,0x80,0x20,0x75,0xA8,0x00,0x00,0x54,0x54,

0x00,0x00,0x04,0x07,0x00,0x03},
{0xAD,0x40,0x10,0x3A,0xD4,0x01,0x03,0xAD,0x40,0x10,0x3A,0xD4,0x01,0x82,0x07,0x5A},
{0x80,0x20,0x75,0xA8,0x02,0x07,0x5A,0x80,0x20,0x75,0xA8,0x00,0x00,0x54,0x54,0xFF}

I want to explain you shortly my application. We have a carrier board for a COMe board and the redriver are placed next to a PCIe x16 connector on our carrier board. The PCIe x16 is splitted into one PCIe x8 and two PCIe x4. We use two DS80PCI800 for the TX and two additional DS80PCI800 for the RX lanes.

The EEPROM data is a little bit formated to have a better overview or to find some special bytes.
The first lanes is the main header and after the main header you can find the data for the 4 redriver (TX lanes first).

I hope you can help me in this matter.

Thanks in advance.
Best regards,
Christian

Hi Lee,

did you have some time to check my EEPROM configuration file?

Regards,
Christian

Christian,

Here are the programming values for the 4 devices.  I found an RXDET[0] bit which did not need to be set.

Device 0  ( EQ = 01,  VOD = 05,  DEM = 02)

00, 00, 04, 07, 00, 01, AD, 40, 00, 1A, D4, 00, 01, AD,

40, 00, 1A, D4, 01, 80, 03, 5A, 80, 00, 35, A8, 00, 03, 

5A, 80, 00, 75, A8, 00, 00, 54, 54

 

Device 1  ( EQ = 01,  VOD = 05,  DEM = 02)

00, 00, 04, 07, 00, 01, AD, 40, 00, 1A, D4, 00, 01, AD,

40, 00, 1A, D4, 01, 80, 03, 5A, 80, 00, 35, A8, 00, 03, 

5A, 80, 00, 75, A8, 00, 00, 54, 54

 

Device 2  ( EQ = 03,  VOD = 05,  DEM = 02)

00, 00, 04, 07, 00, 03, AD, 40, 00, 3A, D4, 00, 03, AD,

40, 00, 3A, D4, 01, 80, 07, 5A, 80, 00, 75, A8, 00, 07,

5A, 80, 00, 75, A8, 00, 00, 54, 54

 

Device 3  ( EQ = 03,  VOD = 05,  DEM = 02)

00, 00, 04, 07, 00, 03, AD, 40, 00, 3A, D4, 00, 03, AD,

40, 00, 3A, D4, 01, 80, 07, 5A, 80, 00, 75, A8, 00, 07,

5A, 80, 00, 75, A8, 00, 00, 54, 54

Regards, 

Lee

Hi Lee,

sorry for the long delay between your last answer and my feedback now.

You are right and now it looks like that the redriver change automatically between the generation 1-3.  Thanks for your help.

Now I have another issue with the redrivers on my PCB.

As I wrote in my previous mails, we have connected the redrivers between a COMe module and a riser board which provides one PCIe x8 and two PCIe x4 connectors for some add-in cards.

Now I try to find out the right redriver configuration to have a working link for PCIe Gen 3 but I have some trouble with the redriver.

If the system is cold (e.g. carrier board temperature next to the redrivers 33°C) I got several times a PCIe x4 link with generation 3.

But if the temperature near to the redrivers rise up to 44°C the same configuration is only PCIe x4 generation 2.

At the moment it's very hard for me to find a working configuration for the redrivers.

Theoretically the redriver should work with an ambient temperature range between -40 and +85°C but at the moment the max ambient temperature on board was 44°C and I have some trouble.

At the moment I have no chance to measure the PCIe signal with a scope to see what's happen with the signal with higher or lower temperature.

Do you have any idea what's happen with the chip if the ambient temperature is higher?

Thanks in advance,

Christian

Hi Christian,

I am not sure how much attenuation is in the channels of the PCIe link.  The equalization and de-emphasis settings are on the higher side of what I would call "typical".  Have you tried lowering the EQ and DEM settings to see if this makes an improvement?

Regards,

Lee

Hi Lee,

thanks for your fast answer.

I tried several configurations for EQ, VOD and DEM round about 250 different configurations.

But often I see that I get a PCIe x4 Gen 3 link if my carrier board has a temperature around 30-35°C but after the carrier board has a 5°C higher temperature the link is no longer Gen 3 but Gen 2.

If a link works fine with a configuration it should be also work with a 5°C higher temp. Or is chip very sensitive and change his performance so much to have another specification with a higher temperature?

At the moment we are not talking about 50 / 60 or 70°C on the carrier board but 40°C should be still a "normal" temperature in the industrial which this redriver should work?

Or do you think it's a problem about the idle voltage or idle gain or something else? With the EEPROM there much more configuration options than with resistors.

We used the DS125BR800 (which is identical, only the range is higher) in the past on another board but with resistor configuration and everything works fine.

But we spend also a lot of time to find the right resistor configuration for this board.

Best regards,

Christian

Hi Christian,

These devices are not very sensitive to temperature change.  Most PCB material will have higher levels of attenuation as the temperature increases.  What length are the traces on the inputs and outputs of the DS80PCI800? 

If you have estimates of the attenuation on these channels it would be helpful to better understand the system.

Regards,

Lee

Hi Lee,

hmm okay.

Find below the path length of the different channels:

TX Channels

COMe (TX Output) ]      ----->       ~170mm      -----> [ Redriver Input // Redriver Output ]      ----->      ~74mm      ----->        PCIe x8 connector

COMe (TX Output) ]      ----->       ~170mm      -----> [ Redriver Input // Redriver Output ]      ----->      ~111mm      ----->      PCIe x4 connector

COMe (TX Output) ]      ----->       ~170mm      -----> [ Redriver Input // Redriver Output ]      ----->      ~87mm      ----->        PCIe x4 connector

RX Channels:

COMe (RX Input) ]      <-----       ~207mm      <----- [ Redriver Output // Redriver Input ]      <-----      ~75mm      <-----        PCIe x8 connector

COMe (RX Input) ]      <-----       ~207mm      <----- [ Redriver Output // Redriver Input ]      <-----      ~104mm     <-----       PCIe x4 connector

COMe (RX Input) ]      <-----       ~207mm      <----- [ Redriver Output // Redriver Input ]      <-----      ~87,7mm     <-----       PCIe x4 connector

Regards,

Christian