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HELP! PIC18F8722 Port F Input Problem

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,

Reply to
GaryI
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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

Reply to
BobW

Hi,

Thanks for the reply.

As I've mentioned the hardware is setup correctly.

Any ideas?

Reply to
GaryI

all are ok.....

so now?

Reply to
GaryI

GaryI wrote in news:6db163e0-c1b4-47d1-9068- snipped-for-privacy@34g2000hsz.googlegroups.com:

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??

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Scott
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Reply to
Scott Seidman

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

Reply to
GaryI

GaryI wrote in news:6e6fdbdc-8783-4c41-93e4- snipped-for-privacy@e6g2000prf.googlegroups.com:

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

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Scott
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Reply to
Scott Seidman

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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Reply to
Spehro Pefhany

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,

Reply to
GaryI

GaryI wrote in news:0838dd5b-61d4-4494-99ec- 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.

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Scott
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Reply to
Scott Seidman

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