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February 19, 2008, 11:51 am

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

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
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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:

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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Scott
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