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Pull Up on PORTa

 
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vtrx



Joined: 11 Oct 2017
Posts: 141

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Pull Up on PORTa
PostPosted: Tue Aug 20, 2019 7:58 pm     Reply with quote
If i use a 47K resistor as pull up on PORTa will the digital input be unstable?
I intend to use ADC or Digital Input on the same pin, selected by software.
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Wed Aug 21, 2019 12:35 am     Reply with quote
Depends totally on your environment.

47K is adequate to 'pull up' a digital signal that is only using relatively low
signal capacitance (so a short line), and not requiring fast slew rates (so
not trying to send fast edges). Remember as well that the analog signal
(when enabled), needs to meet the ADC impedance requirements, and will
be driving into this pull up. How do you visualise switching these signals?.
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