Honored ContributorHI ALL
I'm using the cycloneII(EP2C20Q240C8).I want to know what the difference the pin 178 and the others.when i use the pin 178 as LVTTL output,it cannot output a wave (frequency about 25MHz when i use crystal about 50Mhz),but when i use other pin,they can do it.why??? THE wave mentioned above is that i see by the signal-tap. what can i do to solve it?
Honored ContributorPin 178 can be either normal IO or the output of a pll: PLL2_OUTn. Are you driving this pin from logic (e.g as the output of a divider) or directly from the pll? In the latter case it doesn't work: see page 20 of "Pin Information for the Cyclone® II EP2C15A, EP2C20 and EP2C20A Devices.pdf" (http://www.altera.com/literature/dp/cyclone2/ep2c20_ep2c15a_ep2c20a.pdf).
Honored Contributorno,we just use it as normal IO,as the ADC's control clock,frequency about 25MHz .when we use other IO,it can work well,but when we use then pin178,it cannot output the right wave. i'm so confused!
Honored ContributorThere should be no reason why pin 178 wouldn't function as you want it to.
I suspect you have a either a short between pin 178 and ground, or you are not looking at the right pin (because of a routing swap or so), or because in the logic project the signal is not placed on that pin.Honored Contributorthank you for your answer,but i have tried in two pcb.the first doubt can be excluded. the second doubt: i check the pin many times.
but i have done another experiment, i use the pin178 to output other slow signal, it can do it.so??????Honored ContributorThe reason must then be searched in the logic. If you say that pin 178 outputs a 'slow' signal, how slow is this then? I suggest you make a small project that only drives this pin as the output of a counter? In fact this morning I did make such a small project to simulate to some extent what you are doing, so I just add the .qar for your perusal.
Honored Contributorthank you for your hard work again!
the attachments is my code, can you find some errors for me???thanks a lot!! the ad_clk is assigned to the pin178.Honored ContributorI did a quick compile/simulate on your file and see no reason why the signal does not appear on pin 178. I attach the .qar for your perusal.
Honored ContributorI also didn't find out any problem by simulation, but when i use the signal-tap to watch the ad_clk on the pin178 i find that the program became wrong. The right output wave is like the attachment.
Two years ago, my another colleague also find some problem when he used the EP2C20Q240C8 in other project.he also solved the problem by swapping the pin.Honored ContributorYou didn't say a word about SignalTap in your original post! Did you check at all, if the pin is working correct without connecting SignalTap logic to it? If so, it's a completely different topic in my opinion.
Honored Contributoryou mean the signal tap is unbelieveable?? i will have a try next week. thanks!
