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From: colin@vu-vlsi.UUCP (Colin Kelley)
Newsgroups: sci.electronics,comp.misc,comp.sys.cbm
Subject: Re: SmartWatctch Help
Message-ID: <821@vu-vlsi.UUCP>
Date: Sun, 10-May-87 23:32:14 EDT
Article-I.D.: vu-vlsi.821
Posted: Sun May 10 23:32:14 1987
Date-Received: Wed, 13-May-87 01:04:57 EDT
References: <849@killer.UUCP>
Reply-To: colin@vu-vlsi.UUCP (Colin Kelley)
Organization: Villanova Univ. EE Dept.
Lines: 32
Xref: mnetor sci.electronics:689 comp.misc:501 comp.sys.cbm:431

In article <849@killer.UUCP> sentinel@killer.UUCP (The Sentinel) writes:
>
> I recently picked up a Dallas Semiconductor SmartWatch...[called SW below]
> This is a "no-slot clock" which plugs
>into the board underneath a ROM, and is transparent until you need it.

I've been toying with the same thing--I've been trying to install the
SmartWatch in my PClone.  The problem is:  the SW is intended for a RAM,
not a ROM.  Fortunately the pin-outs are virtually identical.  However,
the SW documentation says that it looks for the 64-bit pattern on D0
while CE* (Chip Enable) and WE* (Write Enable) are both asserted (low).
I had to bend the WE* pin on the SW and connect it directly to the
microprocessor WR*, since that pin was PGM* on the ROM and had been tied
high.  (You ordinarily can't write to those ROMs you know :-)  On both the
ROMs in my system, the designers chose to tie CE* permanently low and just
deal with OE*, which I believe is the only remaining barrier to getting my
SW to work.  If I can get the CE* to be decoded also (maybe just tie CE* and
OE* together, although the timing might be a little tight) I think it'll
work...

I assume the reason you're trying this that you (like me) have seen the
adds for the "Slotless Clock" in computer magazines, and it's clearly a Dallas
Semiconductor product.  I assume that they've modified it slighty to work
with ROMs.  My guess is that they use A0 instead of D0, and OE* instead of CE*,
so that the software only has to READ from 64 magic locations in sequence
rather than write 64 magic values in sequence.  Anyone know for sure?

If all else fails, I'm considering wire-wrapping a little static RAM board
just so I can get at the clock.  I'm sure I can find something to put in 2K
(or 8K) of non-volatile RAM!

	-Colin Kelley  ..{cbmvax,pyrnj,bpa}!vu-vlsi!colin