MachXO external clock question

sgergo said:

Hi!

I'm a beginner in programmable logic and I'm trying to learn by experimenting on small projects using a Lattice MachXO Breakout Board which has MachXO2280 sitting on it. Unfortunately, MachXO seems to changed to NRND thus there is not much documentation around and the Lattice site is pretty poor too. I'm using Lattice Diamond as an IDE.

I'd like to use an external clock source - a 25 MHz TCXO - as the primary clock source of the CPLD. What I can do now is to feed the oscillator output into a random I/O pins and it is all well but I learned that I should feed the external clock signal into a dedicated clock pins to get a nice, undelayed clock signal Indeed, there are PCLK pins but I'm not sure how to configure them: it is just hooking up the TCXO's output to any of the PCLK pins and selecting that pin in the spreadsheet or is there anything else to change in Diamond? Since there are no examples I'd be really appreciated if someone could help. Thank you!

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aruipksni said:

yes you need to connect to the closest dedicated clock pad if possible. then you can use internal PLL.

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mrflibble said:

You usually have a constraint file that tells the tools what net to connect to what IO pin, and also what signal standard etc to use...

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