Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!west!texsun!csccat!ncmicro!ltf
From: ltf@ncmicro.lonestar.org (Lance Franklin)
Newsgroups: sci.electronics
Subject: Re: Dallas Semi Intelligent Sockets?
Message-ID: <274@ncmicro.lonestar.org>
Date: 29 Jan 91 00:08:44 GMT
References: <3222@naucse.cse.nau.edu> <1991Jan28.083000.28601@ims.alaska.edu>
Organization: NC Microproducts, Inc. Richardson, Tx
Lines: 34

In article <1991Jan28.083000.28601@ims.alaska.edu> ftpam1@acad3.alaska.edu writes:
}In article <3222@naucse.cse.nau.edu>, rrw@naucse.cse.nau.edu (Robert Wier) writes...
}
}[query concerning Dallas NVRAM's and SmartSockets delete]
}
}     All of these devices (and EEPROM's as well) share a common problem:  the
}microprocessor accessing them can go berzerk on power-up and especially power-
}down conditions.  I have even seen this with serial EEPROM's that have an
}extremely complicated access protocol.  The Motorola 68HC11 single chip
}microcomputer with internal EEPROM also suffers from this problem.

I beleive Dallas Semiconductor has a solution for this as well...
Their MicroMonitor chip (DS1232) monitors the power status via a
"precision temperature compensated reference and comparator circuit".
An out-of-tolerance condition generates an internal power fail signal
and forces reset to the active state.  A return to in-tolerance
condition keeps the reset signal active for 250ms to allow the power
supply and processor to stablilize.  It also includes a debounced input
for a reset switch and a watchdog timer that will reset the processor if
it's not pinged at a given interval (150ms, 600ms or 1.2seconds).
Voltage tolerance is settable to either 5% or 10%.

Another chip, the Power Monitor (DS1231) is similar, but will provide
a warning before hitting reset, doesn't have the watchdog timer or reset
switch circuitry and is evidently designed to replace standard power-up
reset circuitry. 

Lance

-- 
Lance T. Franklin            +----------------------------------------------+
(ltf@ncmicro.lonestar.org)   | "You want I should bop you with this here    |
NC Microproducts, Inc.       |    Lollipop?!?"                 The Fat Fury |
Richardson, Texas            +----------------------------------------------+