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From: | Dan |
Subject: | Re: [avr-chat] Crystals (was ATmega32 @ 16MHz : fuse bits ??) |
Date: | Thu, 17 Nov 2005 07:41:15 -0500 |
User-agent: | Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.3) Gecko/20040910 |
Hi, I'm new to the list but have been using Atmel for a long time. I'm glad I found this. This convention dates back to the first PROMs and EPROMs. Where the cell of each data bit was actually a type of fuse which literally gets burned (or popped) by using a higher programming voltage. So the unprogrammed state was actually a 'closed' connection, thus creating a logic 1 as if you the switch was closed until you opened it. This convention has remained intact over 30yrs year now. IIWDTI =Dan .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. [My Corner of Cyberspace http://ragooman.home.comcast.net/ ] [Pittsburgh Robotics Society Got Robot? http://www.pghrobotics.org/ ] [Pittsburgh Vintage Comp.Society http://groups.yahoo.com/group/pghvintagecomp/ ] .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. Joerg Wunsch wrote:
Vincent Trouilliez <address@hidden> wrote:About the fuse bits that have a reversed logic, I am not sure why the data sheet keeps insisting that 0 means programmed and 1 unprogrammed.
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