09-28-2012 02:59 AM
I will design a XC7VX690T board, but the GTXs of it are of no use for me.
Should I still provide the power for them?
09-28-2012 08:42 AM
Good question: I do not seem to find the recommendation for what to do with the power pins on used GTX in 7-series.
Other families have this information in their user's guides, or in the technical answers....
File a webcase, as the information seems to be missing from the GTX user' guide (I couldn't find it).
Hopefully, someone else will read this and reply with the answer (but a webcase is faster, and guaranteed to get an answer).
09-28-2012 10:23 AM
The 7 Series GTX/GTH User Guide UG476 documents what should be done for each power supply rail if the MGT quads are unused in Table 5-5.
09-28-2012 10:27 AM
This is actually covered in user guide, e.g.
http://www.xilinx.com/support/documentation/user_guides/ug476_7Series_Transceivers.pdf (7 Series FPGAs GTX/GTH Transceivers User Guide)
I do remember it being easier to find on previous families (e.g. V5) because of the way the data was presented and I could quickly get there by searching for "unused".
The magical search term here is "not used" - search for these occurrences to skip through the 494 pages more quickly.
BTW, the 7VX690T uses the GTH transceiver not the GTX transceiver (that is used on the 7VX485T, 7V2000T, Kintex-7, etc.) Which is very similar but enhanced in a number of respects including DFE.
09-28-2012 10:36 AM
I missed that. I (thought I) read through that table, but I missed it (the first time). You are right: it is there.
Each power supply, if not used, has its own note on where and what one should do with those pins.
Perhaps we need a technical answer to point to this table? All the earlier parts either have a specific answer, or an answer pointing to the right document (table number, page number). Series-7 seems to not be included for some reason in these answers.
Not sure how we can make this easier for designers. The general rule is read the user's guide, and read any pcb layout specific guidelines or checklists. I believe that to still be true.
My mistake was using the search line in adobe acrobat. I did not choose to search for the same string that was used in that table.
"unused power" "unused gtx" "unused" -- there are many options, and perhaps one just has to read the manual.
12-04-2012 04:51 PM
I am still a bit confused by the 7 Series GTX/GTH Transceiver Guide's comment about "not used" transceivers.
My design XC7K160T-1FFG676 has no need for GTX/GTH and will not be using any of those IO or Clocks, etc. So, from the Analog Power Supply Pins section we find:
"If all of the Quads in a power supply group are not used, the associated power pins can be left unconnected or tied to ground (unless the RCAL circuit is in that Quad)."
I can suppose that there are referring to large devices with multiple quads. However I get stuck later regarding RCAL circuit with:
"The RCAL circuit performs the resistor calibration only during
configuration of the FPGA. Prior to configuration, all analog supply voltages must be
present and within the proper tolerance as specified in the respective 7 series FPGAs data
The RCAL circuit is associated with the GTX/GTH transceiver Quad that is the RCAL
master. The RCAL master performs the termination resistor calibration during
configuration of the FPGA"
Will I get stuck in configuration if all MGTAVCC, MGTAVTT, MGTVCCAUX, MGTXTX, MGTXRX, MGTAVTTRCAL, and MGTREFCLK are not connected?
Thanks in advance,
01-04-2013 01:28 PM
I can confirm that all the GTX power and IO (i.e. all pins starting with MGT, including RCAL) can be left un-connected on a Kintex 7 160 if you will not be using any of the features. My board configures fine and appears to opperate without issue.