AVR-Chat

Hello Hein,

Yes, sorry... we drifted away from your problem but it was an interesting
discussion between Jose and I.

Delighted that you were able to find and fix the problem but it is
mysterious just why. I drive 74HC chips in several production environments
without problem using AVR processors, ATmega32 and ATmega644 on one such and
ATmega2560 the other.

Maybe someone will enlighten us on just how this happens as it seems odd to
me that a just a high value resistance pull down would be required. Wonder
if others have had this problem?

Jim


----- Original Message ----- 
From: "kernels_nz" <hein@mediflex.co.nz>
To: <AVR-Chat@yahoogroups.com>
Sent: Monday, April 03, 2006 1:41 PM
Subject: [AVR-Chat] Re: Connecting AVRs directly to inputs of 74HC and LS
logic chips.


Hmmhm, discussion seems to have strayed a bit, but just in case
anyone ever runs across the same problem:

* I definately had the pins on the AVRs configured as outputs.

* The same fault occured with both 74HC and 74LS chips, but only on
   my newer batches of Mega16s and Tiny26s.

* In both cases, the problem was cured by fitting external 100k
  pulldown resistors. NO CODE CHANGES.

* I know it sounds like I had the pins configured as inputs and using
  the internal pullup to pull it high, but thats just not the case.

Cheers
Hein B

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