Transceiver Toolkit Loopback modes

[HBhat2]

Hi,

I am using transceiver toolkit on Stratix 10 SoC Dev kit to check the transceiver line performance.

Under Loopback mode option I am seeing 4 options

Off

Metallic

Reverse Serial

Serial Loopback

I understood Off and Serial Loopback options.

For "Reverse serial", I know that this is supported for GX data rates and not for GXT data rates. But the L-tile user guide mentions 2 types of reverse serial namely i) Pre-CDR and ii) post CDR. So, regarding Reverse Serial mode, I want to know how will I come to know that "reverse serial" is pre CDR or Post CDR?

Also, I didn't get any info regarding Metallic mode. What is the use of metallic mode and how it is different from serial loopback?

With regards,

HPB

[CheePin_C_Intel]

Hi HPB,

As I understand it, you have some inquiries related to the loopback option as in the TTK. Please see my response as following:

1. reverse serial - sorry for the confusion. There seems to be no specific detail on whether it is pre or post CDR. However, based on my understanding, it is pre-CDR loopback. You may try to dump out the register value of the Native PHY and cross check with those mentioned in section "A.4.4. Loopback" of the S10 L and H tile XCVR PHY user guide.

2. metallic - Sorry as there is no specific detail that I could find on this. Based on my experience, I will use serial loopback. Sorry for the inconvenience.

Please let me know if there is any concern. Thank you.

Best regards,

Chee Pin

[HBhat2]

Hi Chee Pin,

Thanks for the response. If you came across "metallic" mode in future, please update me.

With Regards,

HPB

[CheePin_C_Intel]

Sure. I will update you if there I come across any detail on the metallic mode in future. thank you.

[HBhat2]

Hi,

Also, I noticed that in the L tile userguide there is a note under 5.9. Loopback Modes chapter

Note: Intel Stratix 10 transceiver channels configured in GXT mode do not support Pre-CDR reverse serial loopback and Post-CDR reverse serial loopback.

When I open the toolkit and the toolkit shows the data rate to be 20.625Gbps, but reverse-Serial Loopback option is still available with the dropdown button.

With Regards,

HPB

[CheePin_C_Intel]

Hi HPB,

Thanks for your update. Regarding your latest note, I would recommend to follow the user guide. For GXT channels, it does not support reverse serial loopback. 

Thank you.

[HBhat2]

Hi @cheepinc_Intel​ ,

One more clarification required regarding basic Loopback concept.

Till now I have done Loopback for TX to RX in the same Channel. For example, Bank 1D Channel 0 - TX0 to RX0 (Channel 0 TX to RX) loopback done and tested.

Is it possible to Loopback between different channels ? For example, Bank 1D- TX0 to RX1 (Loopback from Channel 0 TX to Channel 1 RX)?

With Regards,

HPB

[CheePin_C_Intel]

Hi HPB,

Regarding your latest inquiry on the loopback between different channels, sorry as this is not supported due to hardware architecture. The internal loopback path is available only within the same channel. Sorry for the inconvenience.

[HBhat2]

Hi,

Thanks for your input. I was just checking the possibility of loopback between 2 different channels. Also, in the user guide, I have not found the information that Loopback modes supported within the channel only.

With Regards,

HPB

[CheePin_C_Intel]

Hi HPB,

Sorry for the inconvenience due to the user guide.