I think the variation with voltage and temperature will be quite large.
I agree. I think almost all FPGAs have an internal RC-oscillator used for configuration. In MAXII (not really an FPGA but also not really a CPLD...) e.g., I know it is accessible, but is it also accessible in other families? Of course there are also people out there building ring-oscillators, but there you have almost no guarentee regarding frequency at all..
Thomas
Thomas Entner schrieb:
Hi Thomas,
the internal oscillators are present in almost all fpga families but they are not accessible in all of them. However this is not a big problem on-chip oscillators can be utilized in any FPGAs. Their implementation is usually family dependant and may require some tricks.
for s3,s3e,v4 it is also possible to use the DCM in as on-chip free running oscillators by enabling factory test mode.
Antti
Hi Antti, Is that feature documented anywhere? Or is this a task for my FAE? Thanks, Syms.
Symon schrieb:
I dont think your FAE does know it. unless his name is Ken Chapman!
there is some documentation in Spartan3e reference designs docs. the useage for Virtex-4 is a little bit different and only in
Antti
Symon schrieb:
now the V4 is also docu :) Antti
Many thanks! Syms.
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