SERDES ibert测试

Serdes问题

1. Ibert回环测试问题
2. IBERT回环测试near-end-pcs误码率比near-end-pma误码率更高的问题。

AR# 53107 7 Series GTX/GTH Transceivers - Recommended usage in Near End PCS loopback mode

Description
This answer record provides guidelines to use 7 series GTX/GTH transceivers in PCS loopback mode.
Solution
In PCS loopback mode, if there is no connection from TXP/TXN to RXP/RXN, then RXRECCLK output from CDR is not expected to be good.
This is due to a lack of data transitions at the input to lock to.
If a design requires RXRECCLK for its fabric logic, the design can fail.
For these designs, it is recommended to use CDR in “lock to reference” mode.
Follow the steps below to make sure that the CDR is in “lock to reference” mode:
Step1: Drive the following signals
Set RXOUTCLKSEL to select RXOUTCLKPCS,

(OR)

Set RXCDRHOLD to 1’b1 and RXCDROVRDEN to 1’b0

Step2: Perform a full RX reset of the transceiver
Pulse GTRXRESET
If a design does not use RXRECCLK for fabric logic, only Step 2 is required.

AR# 34203 11.x ChipScope - IBERT - Spartan-6, Virtex-5, Virtex-6 - PCS loopback results in an increasing error count
Description
When I set my GT to near-end PCS loopback, I see the bit error rate increasing. Is there an issue with my device?
Solution
This is a result of clock settings in the core. As a work-around, use PMA near-end loopback. Alternatively, you canchange the Loopback mode to Near-End PMA and then change back to Near-End PCS. Reset Error count and note that no errors occur.

1. FAR-END-PCS和far-end-pma测试软件界面设置问题。
   
   因此，
   1.左边FPGA RX端观测far-end-pma时，左边FPGA设置为none模式，这时候信号从左边FPGA tx pin端口发送到右边FPGA，在右边FPGA中设置为far-end-pma.
   2.左边FPGA RX端观测far-end-pcs时，左边FPGA设置为none模式，这时候信号从左边FPGA tx pin端口发送到右边FPGA，在右边FPGA中设置为far-end-pcs.
   3.如果右边不是fpga，比如一个光纤或是背板时，左边设置为none，右边就外部直接回环了。
2. Ibert测试vivado与ISE异同问题。

对于IBERT测试时，NEAR-END-PCS误码率比near-end-pma误码率高问题，提到的rxusrclk的时钟设置方法。其中在ISE下面ibert有可设置的DRP界面，但是VIVADO下面已经没有了。

HTG813与HTG814相关问题
注意HTG813是48路光路TX，而HTG814是48路光路RX，当他们直接相连进行外部回环ibert测试时，光路TX1对应光路RX12，而非TX1对应RX1.

Gth调试问题
后面调试碰到问题再贴上来吧。