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Carry chain on Cyclone V

Altera_Forum
Honored Contributor II
‎01-19-2016 12:43 AM
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Hi, 

I'm new and I have a problem with implementation carry chain in Cyclone V. I have to make a ring oscillator on this line and I have a problem with which component should I use ?  

I think about component carry_sum or lpm_add_sub. 

Also I have a problem with carry_sum. In quartus prime this buffers carry_sum are ignored and nothing. Do you have any suggestion ? :confused::confused:
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Altera_Forum
Honored Contributor II
‎01-19-2016 05:08 AM
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I would do your best to avoid putting a ring oscillator in an FPGA. They're difficult to do and timing gives them a huge variation over PVT, making them not very reliable. That being said, sometimes there is a good reason and I put together the following design. Hopefully it helps. 

http://www.alterawiki.com/wiki/ring_oscillator
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