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john66
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| Unused ADC pins |
 Posted: Sat Oct 16, 2004 10:25 am |
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I am debugging someone else's design using the PIC16C73. Port A is set up as all analog but there are three unconnected pins on the port. I have seen unconnected digital inputs create nasty, intermittent problems.
Has anyone experienced the same type of trouble with unconnected ADC inputs? |
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Ttelmah
Guest
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| Re: Unused ADC pins |
| Posted: Sat Oct 16, 2004 3:09 pm |
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| john66 wrote: | I am debugging someone else's design using the PIC16C73. Port A is set up as all analog but there are three unconnected pins on the port. I have seen unconnected digital inputs create nasty, intermittent problems.
Has anyone experienced the same type of trouble with unconnected ADC inputs? |
I don't think this would be a problem.
The problem with digital inputs, is they get into the 'transition' area, where they are undecided about whether to be high or low, and can draw excessive current in this area. This is why the act of selecting the ADC, turns off the digital input buffers on the selected pins. The pins are still protected by the clamp diodes, so should be OK. Personally, I'd still clamp the pins, but the normal digital problems should not apply.
Best Wishes |
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Guest
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| Posted: Sat Oct 16, 2004 3:44 pm |
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| That makes sense. Thanks. |
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Guest
Guest
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| Unused pins in general |
| Posted: Mon Oct 18, 2004 12:05 am |
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| OK, I'll bite: what should one do with unused digital I/O pins? Make 'em inputs and set 'em high? Make 'em outputs and leave them unconnected? |
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Haplo
Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia
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| Re: Unused pins in general |
| Posted: Mon Oct 18, 2004 12:23 am |
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| Guest wrote: | | OK, I'll bite: what should one do with unused digital I/O pins? Make 'em inputs and set 'em high? |
How about making them outputs and setting them high? 
That's probably the best way of doing it, making them outputs and setting them either to high or low. Or you can make them inputs and tie them to VCC or GND via resistors. |
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