Migrating from XEM3010 to XEM6010 - differential signal pair compatibility

Spartan-6 USB 2.0 Modules
1

Hi,

I’ve an existing system I’d like to migrate from the XEM3010 to the XEM6010. My PCB has many differential pairs hardwired into it, which match the necessary differential pairs on the XEM3010. However, I’ve noticed a lot of the differential pairings do not match those on the XEM6010.

It appears the XEM6010 and XEM3010 share differential pairings until connector pins 45 and 46, after which the differential pins become mismatched between the modules. Some examples:

Matched differential pairs before connector pins 45/46:

  • XEM3010 - JP3 pins 41 and 43 = differential pair L39N and L39P, respectively
  • XEM6010 - JP3 pins 41 and 43 = differential pair L61P and L61N, respectively
Note also the polarity mismatch (L39N connects to L61P). However, swapping differential pin polarity is readily done in the FPGA (see Xilinx xapp491).

Mis-matched differential pairs after connector pins 45/46:

  • XEM3010 - JP3 pins 47 and 49 = differential pair L40N and L40P, respectively
  • XEM6010 - JP3 pins 47 and 49 = non-pair L03N and L01P, respectively

Opal Kelly - Please could you check whether the mismatches I’ve identified are indeed mismatches, and not typos in the UM?

I appreciate your efforts to make the XEM6010 as compatible as possible with the XEM3010. However, if these are mismatches, my PCB will need redesigned to work with the XEM6010. Also, I think a quick note mentioning these mismatches would be helpful in the UM section, “Migrating from the XEM3010 to the XEM6010”.

Thanks very much and I look forward to your response.

Keith.

2

Hi Keith,

that seems a bit troubling. I’m also worried why Opal Kelly Support hasn’t responded yet. What is the current status? Did you have to redesign the PCB?

Cheers, Max

3

When migrating from one generation of FPGAs to another, it’s not always possible to build an exactly compatible product. There are a myriad ways that the I/Os may be applied and while we certainly may have made a compatible product for your specific application, that may have broken compatibility for others. So we endeavor to do the best we can and reduce the impact on the peripheral as much as possible.

These are not typos in the XEM6010 User’s Manual.

Also, please note that these forums are intended as a community forum. We try to follow them but occasionally will miss a post. For pressing matters that require a response from us (and not some other user of our products) always contact [email protected]. That is a much more reliable venue for direct technical support from Opal Kelly.