"destructive read"

Bob Bradlee caveguy at sbcglobal.net
Mon Oct 1 09:16:34 CDT 2007

I am aware of some problems with poorly sequenced devices that would fail over time from the constant 
abuse. Mixing ttl logic with opencollector devices was still a neat idea to keep a mininum chip count about 
the time those monitors were designed. During powerup ttl devices were trying to push a 1 onto a buss 
where several opencollector devices trying to pull the buss to ground at the same time. A lot of things 
happen in those first clock cycles on powerup, before everything falls into sync. 

The other Bob

On Mon, 1 Oct 2007 06:40:00 -0700 (GMT-07:00), Steve Thatcher wrote:

>the "destructive read" could have been a design issue where the ROM outputs are enabled while some 
other output drive is attempting to use the data bus. The ROM output drivers may well fail after repeatedly 
being abused like this.

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