HELP! PIC18F8722 Port F Input Problem

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Hi,



I'm using the 18f8722.  What I've noticed is that when I power up the
device and try to read Port F, I do not get anything back from pin 7
until after a few seconds of waiting. The circuit is fine, and the
port f pin 7 works fine on some hardware and this problem occurs on
other.  There's some kind of pic hardware issue with the functionality
of using pins 5/6/7 on port f.  I've done some testing and debugging
by moving lines to different pins but I've noticed that there's some
'correlation' between pins 5/6/7 on portf.



It all points towards a silicon issue possibly with the pic and has
yet to be reported by Microchip.  There's no info on the Silicon
Errata datasheets.



Help greatly appreciated!



Regards,




Re: HELP! PIC18F8722 Port F Input Problem



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You need to be absolutely certain that you're meeting valid Vil and Vih on
all the inputs. If you haven't already done so, read the datasheet
carefully.

Bob



Re: HELP! PIC18F8722 Port F Input Problem


Hi,

Thanks for the reply.

As I've mentioned the hardware is setup correctly.

Any ideas?

Re: HELP! PIC18F8722 Port F Input Problem


all are ok.....

so now?

Re: HELP! PIC18F8722 Port F Input Problem


snipped-for-privacy@34g2000hsz.googlegroups.com:

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What does this mean?  It works on some ucontrollers, but not on others, or
it works with some circuits on the same controller, but not all??


--
Scott
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Re: HELP! PIC18F8722 Port F Input Problem


there are several boards the pic18f8722 is used on - and the delay
from "power-on to read" on poft f pin 7 'RF7' on one board is
different to another -

i.e.

a) on one board i hold a sw connected to RF7 and it takes about 10
secs before i get a correct read from pin 7,

b) on there boards theres no problem at all i perss the sw on RF7 and
read what i expect instantly,

c) whilst on another board which has an 8772, i hold a sw connected to
RF7 and it takes about 5 secs before i get a correct read from pin 7,

There a several boards which use various pics i.e. 2550, 452, but only
the 8772 seems to have this behaviour.

regards



Re: HELP! PIC18F8722 Port F Input Problem


snipped-for-privacy@e6g2000prf.googlegroups.com:

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I'm still having a hard time understanding.  Is this a "power-on-to-read"
problem, or a general slow read on port F?



--
Scott
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Re: HELP! PIC18F8722 Port F Input Problem


On Tue, 19 Feb 2008 03:51:52 -0800 (PST), the renowned GaryI

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Do you have a pull-up or pull-down resistor? Have you configured the
port pins as digital inputs using ADCON1?  Have you verified that
ADCON1 is set correctly using a debugger?


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: HELP! PIC18F8722 Port F Input Problem


Read my message.... I connect directly to pin RF7 on the pic!!!!!
there's no pull downs up or anything else for that matter.... ALL and
i mean and know ALL registers are setup CORRECTLY!

Basically when the pic is powered theres a delay before i see anything
directly on that pin - as detailed in post dated '20 Feb, 15:27'

This pic is only couple of years old since design - looks like a
possible silicon issue!

Regards,


Re: HELP! PIC18F8722 Port F Input Problem


snipped-for-privacy@o77g2000hsf.googlegroups.com:

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What is the spec for this property?  If there is none, then you can't
design a system that counts on it.  You might look into any supervisory
chips that are in your system as well.


--
Scott
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