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Altera_Forum
Honored Contributor
18 years agocan be LVTTL input while LVDS output using PLL?
The input clock of PLL is LVTTL and PLL LVDS output in enhanced mode as pic posted above. http://photos.i.cn.yahoo.com/04400327037/2bdc/9e75.jpg/ (http://photos.i.cn.yahoo.com/04400327037/2bdc/9e7...
Altera_Forum
Honored Contributor
18 years agoHello,
Also this file isn't accessible to me. Generally, LVDS outputs have a fixed drive strength and no optional terminations, when using LVDS capable outputs, I think. (You don't tell the used FPGA family). There has been an issue when using single ended clock input with differential outputs of a PLL, it has been discussed of few months ago. Quartus place&route didn't accept it. This is a bug to my opinion, but I don't know if changes to Quartus have been applied and if all FPGA families are affected. In one case, explicite instantiation of a clock control block could help. I believe, that the answer to your question is yes, by specification. If you don't find a way to make Quartus accept this combination, ask Altera support how to. Regards, Frank