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Altera_Forum
Honored Contributor
Honored ContributorExternal trigger so easy?
I just want to use the signal generator to trigger one IO pin of FPGA externally. On FPGA , this trigger sigal will be captured on the rising edge.
But, when I just connect the IO pin on FPGA to the cable which will be connected to the sigal generator or oscillograph, the trigger starts, it works so easy that I can't control it, what's interesting is that it works even when I toutch the pin. Then I measure the voltage of my fingers which is about 500 mV. FPGA Information: LVTTL selected, 10 pf loaded, dual-in-line pin used as the input trigger. Does anybody kind of use external trigger, and know why this happened? John11 Replies
Altera_Forum:) http://img822.imageshack.us/i/fpga.jpg/ (http://img822.imageshack.us/i/fpga.jpg/)
Now ,I will ask is the circuit like this- Altera_Forum--- Quote Start --- Aha, that's funny! How to upload picture? --- Quote End --- http://imageshack.us/
- Altera_Forum
- Altera_Forum--- Quote Start --- The circuit is like this?file:///C:/DOCUME~1/john/LOCALS~1/Temp/]%60@4C)%7BKA%7DYCJN@K9%7BI~LJG.jpg --- Quote End --- Sorry. I can't hack you computer. :)
- Altera_Forum
The circuit is like this?file:///C:/DOCUME~1/john/LOCALS~1/Temp/]%60@4C)%7BKA%7DYCJN@K9%7BI~LJG.jpg
- Altera_Forum--- Quote Start --- I use oscillograph to measure max voltage. What's wrong? --- Quote End --- Set oscillograph in waiting mode. Use probe with low input capacitance. If you have a cat, play with them. After, touch a probe.
- Altera_Forum
I use oscillograph to measure max voltage. What's wrong?
- Altera_Forum--- Quote Start --- So, why just 500 mV --- Quote End --- Because you measuring wrong. How you measure 500mv?
- Altera_Forum
Thanks ,Ton and BOND! Good advice for me! Really appreciatate that!
So, why just 500 mV can do the things that 3 V or some can do? IS it because electromagnetic interface, for that float pins can be affected larger interface than others? - Altera_Forum--- Quote Start --- pair of protection diodes from board input to power and ground (BAV99). --- Quote End --- TVS diode is better solution now. http://en.wikipedia.org/wiki/transient_voltage_suppression_diode http://www.vishay.com/diodes/list/product-81673/
