Electronic – the meaning of speed grade marking on Xilinx FPGAs

fpgafrequencymarkingsspartanxilinx

According to Xilinx FPGA product datasheets, the numbers on the 5th line as 4C or 5I stand for speed grade and temperature.I have a XC3S400 with 4C speed grade (4= standard speed, 5= High performance).

I want to know what exactly the standard speed grade means ? Can I relate it to a specific bandwidth? For example assume I want to make a high speed counter and want to use the maximum possible speed driven from a crystal oscillator into GCKx pins. Can I use this 4C marking as a guide for crystal oscillator selection?

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Best Answer

The speed grade has to do mostly with specified transistor switching speed. You can review the definition of -MIN, -4 and -5 speed grades in appnote 312, page 125 onwards.

This determines how quickly you can run internal clocked circuits. It will not influence the choice of your crystal oscillator, as you will use a PLL multiplier to generate the actual system clock from a realistic crystal frequency.

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Electronic – the file extension of the file that is loaded in a Xilinx FPGA

This file is commonly called a "bitstream". Xilinx devices' bitstreams have the extension '.bit' and are generated by a program called 'bitgen'. '.bit' files are binaries and those are generated by default; if you want the ASCII representation of the bitstream, run

bitgen -b <your design>.ncd

and then a '.rbt' file will be generated in addition to the '.bit' file.

For further information about generating Xilinx bistreams, see Chapter 15 in this user guide for ISE version 12.4:

http://www.xilinx.com/support/documentation/sw_manuals/xilinx12_4/devref.pdf

For more information about Virtex 4 bistreams specifically, see the configuration guide for that device:

http://www.xilinx.com/support/documentation/user_guides/ug071.pdf

Electronic – Xilinx FPGAs – how to demote specific warnings to info or make them disappear

I had this same problem for a long time. Unfortunately there is no good way to change some warnings into info's or some errors into warnings. My problem was that some warnings should have been errors! Some of my FPGA's were generating 5000+ messages and there was no way to wade through them to see which ones were important or not.

In the end, I wrote a program that would read a Xilinx log file and reassign warnings/errors/infos depending on my custom settings. Works great. Too bad I can't make that program public.

Best Answer

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Electronic – the file extension of the file that is loaded in a Xilinx FPGA

Electronic – Xilinx FPGAs – how to demote specific warnings to info or make them disappear

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