SV: [Icc-avr] ATmega8 hardware problem

[Bengt Ragnemalm]

I we assume that you have defined the registers correctly for turning the
pull-ups (the corresponding bit in PORTD shall be set) on I would take a
search in the entire datasheet for the word "pull-up". Check the the
secondary function of the PORT D pins. Some functions may turn pull-ups off.
Or it could be that the internal value are to high (up to 50k).

Also check the status of the PUD bit in SFIOR at the time you use PORTD

Or it could be that the AVR is damaged.

/Bengt

> -----Ursprungligt meddelande-----
> Från: icc-avr-bounces at imagecraft.com [mailto:icc-avr-
> bounces at imagecraft.com] För John Baraclough
> Skickat: den 16 augusti 2008 21:32
> Till: Discussion list for ICCAVR and ICCtiny Users. You do NOT need
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> Ämne: [Icc-avr] ATmega8 hardware problem
> 
> Hi All,
> 
> I've posted this question on AvrFreaks but nobody has replied so I
> thought I would try here.
> 
> I'm using an ATmega8 in a small application with a 10-way DIP switch.
> Six of the switches are on PortC and the internal pull-ups are fine on
> this port. However, the remaining four switches are on Port D and I have
> a problem with getting the internal pull-ups to work on bits 5, 6 7 & 1.
> The data sheet implies that the pull-ups are present on these pins but I
> don't seem to be able to switch them on.
> 
> The problem has been solved by adding external pull-ups to these pins,
> but I'm curious to know if anyone else has had a similar problem.
> 
> All the best for now,
> John
> 
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