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From: stever@videovax.UUCP (Steven E. Rice)
Newsgroups: net.micro.amiga
Subject: Re: Amiga Hardware Wishlist
Message-ID: <1859@videovax.UUCP>
Date: Thu, 24-Jul-86 04:23:01 EDT
Article-I.D.: videovax.1859
Posted: Thu Jul 24 04:23:01 1986
Date-Received: Fri, 25-Jul-86 21:10:06 EDT
References: <815@tekig4.UUCP>
Reply-To: stever@videovax.UUCP (Steven E. Rice)
Organization: Tektronix, Comm Group, TV R&D
Lines: 42
Keywords: clock chip, crystal
Summary: Especially, a nice stable clock

In article <815@tekig4.UUCP>, Brian Rhodefer (brianr@tekig4.UUCP) makes
several suggestions for an Amiga expansion box.  I would like to second
his suggestion for an SCSI interface and suggest a very nice implementation
of another suggestion:

> 4) Has non-volatile timekeeper
>    (e.g. battery-operated CMOS clock/calendar)

There is an extremely nice clock/calendar chip available from GE/Intersil --
I believe the part number is ICL 7170 (I'm typing on my Amiga at home,
so I don't have the data sheet handy!).  It has two features that make it
a real winner:

   1. It requires no external power-switching logic.  The circuitry to
      switch from battery to the +5 volt supply is built in.  All that
      is needed is a battery and a current-limiting resistor (1K to 10K
      or so).  Not only does this save money, it significantly improves
      the chances that the chip will not be reset or otherwise disabled
      by ragged power or switching the power off and on too fast.

   2. It draws extremely small amounts of power, even when running with
      a 1+ MHz crystal.  (There are three or four possible crystal
      frequencies -- 32.768 kHz, 1.048576 MHz, possibly 2.097152 MHz,
      and 4.194304 MHz -- I can't remember if the 2+ MHz frequency is
      there.)  All 32.768 kHz crystals have a significant problem --
      temperature stability (or lack thereof).  Even the poorest 1+ MHz
      crystal should have better frequency stability with temperature.

If this part is combined with a Seiko 1.045876 MHz DS-MGQ crystal, which
has an extremely low temperature coefficient, the clock should keep very
good time.

How about it, guys?  Let's see a really good clock in there. . .

					Steve Rice

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{decvax | hplabs | ihnp4 | uw-beaver}!tektronix!videovax!stever

No, I don't work for GE/Intersil or Seiko.  However, I am using those parts
in a product that will NOT connect to an Amiga expansion bus.  Trademarks
are duly noted. . .