On Sun, 18 Apr 2004 07:50:20 -0500, Edward Gisske wrote:

>I am contemplating using a 16F873A for a project. The circuit needs to have
>one channel of A/D and one comparator and a bunch of digital I/O. After a
>lot of RTFM'ing of the Data Sheet and the Mid-Range reference, I haven't
>been able to devine if it is possible to use port A for A/D, comparator, and
>some digital I/
>O at the same time (different lines of Port A of course). Do the comparator
>inputs have to be designated as A/D inputs in ADCON? How are these functions
>multiplexed?
>

The 873 has 5 A/D channels but it doesn't have any comparators.

You can mix A/D channels with digital I/O by setting ADCON1 bits
(16F87x data sheet, DS30292C, page 112). A setting of 0 configures all
5 port A pins as A/D channels. A setting of 6 or 7 configures all 5
port A pins as digital I/O. The other settings configure the port for
different mixes of A/D inputs, digital I/O, and Vref selections.

Depending on your application, you could perhaps compare an A/D result
to a fixed value to perform as a comparator in software.
Alternatively, you could implement an external hardware comparator and
read its output with a digital I/O pin.


Regards, Bob

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