Electronics > Beginners
RS485 unterminated
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David Hess:

--- Quote from: rakeshm55 on July 07, 2018, 01:26:19 pm ---
--- Quote from: David Hess on July 07, 2018, 10:47:19 am ---Series termination at the source without parallel termination at the load produces a reflection which causes the voltage to initially shift half way.
--- End quote ---

Thanks for pointing the issue....

This half way shift(1.5V) will remain for half of roundtrip time if i am not wrong....Also any voltage above 200mV will be considered as high....On similar lines any diff voltage below -200mV considered as low ... So wont this be ok..or will it be a show stopper....
--- End quote ---

As long as the input threshold requirements of the differential receiver are met it is not a problem.  But for instance if the source termination resistor values were such that the differential voltage was zero volts during the reflection, the differential receiver would have very low noise immunity.
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