Multisim and Ultiboard

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LED changes current value

hi,

 

i have connected a led with 8051 and wrote a simple C program for testing purpose. I found that the LED sometimes turns on and sometimes does not. I placed a probe and the probe reading shows different current values when i change the C program code.

 

For example,

when P20 = 0; in C code I get I(dc) = 1.21pA, V=300mV, V(dc)=0

when P20 = 1; I get I(dc) = 324uA, V = V(dc) = 1.76V

measured at the port's pin

 

The LED current setting is 5mA(the default). Is this peak to peak? or RMS?

 

The 8051 has source current capability of 60uA as I have come to know. Can we check this?

 

Thanks

 

 

 

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Hi sumalama,

 

What version of Multisim are you working on? Can you upload the test schematic that you were doing with the C program?  For the 8051 sourcing capability you can take a look at the specifications of the controller, but I am a little confused with your description so in order to help you better I would like to see if I can reproduce the behavior that you are having.

 

 

Regards,

Sil.VI
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