Voltage Threshold for Wait on Rising Edge function

[Duy2019]

Hello,

Can anybody help me at what voltage level "Wait on Rising Edge" will register as rising edge, i'm using NI Crio 9411 I/O Module.

Thank you!

[JÞB]

That would depend on the supply voltage.  The 9411 will observe a rising edge between a guaranteed logic 0 and 1 but is dependant on the rail voltage to detect the difference. 

As a general rule use 0.707 x Vss

[Duy2019]

hi JPB,

I really appreciate your quick response. I just need some clarifications, i'm interested in voltage threshold level for "Wait on Rising Edge" function, not for the module that it runs on, so i think i should have asked " Does "Wait on Rising Edge" have its own voltage threshold for rising edge?"

  - If YES, then what is it? Our Vss for 9411 is 24V and we currently have +/-2.5V square wave input to 9411. It doesn't meet the general rule (0.707*Vss) but everything works fine (?). Did you mean 0.707*Vinput?

  - If NO, then will "Wait on Rising Edge" use whatever the Logic High/Low range of the module that it runs on? For example, "Wait on Rising Edge" will determine Logic 1 (0.3V-24V) and Logic 0 ((-24V)-(-0.3V)) for differential mode if 9411 is being used?

Thanks again!

Duy

[santo_13]

As per the 9411 datasheet, anything above 2V is considered a high in single ended mode - this is how your +/-2.5V works