31 Dec
2002
31 Dec
'02
3:19 p.m.
A while back I had problems accessing a Grid 1520-286
because of a password. If I remember correctly it was a
DS1287A. The A signified it as resettable and grounding
2 pins cleared the memory. Your problem would seem to
stem more from the BIOS settings and it is going to the
default setting and since the Dallis chip is dead nothing
is retained. ISTR that the 12887 is a drop-in replacement.
If you want to call soldering all those pins "drop-in"
Dallas has a bunch of info on the chip. I don't have the
URL handy.
Considering all the problems and low used prices
involved. You might consider getting an old Grid 1520
which also has the advantage of an additional EPROM
slot which can contain info configuring various aspects of
the computer, including a system boot.
Lawrence
On 31 Dec 2002, , Ethan Dicks wrote:
While attempting to revive a Compaq 286/SLT laptop for use
as a front-end for my UP600a programmer, I have found that
the battery on the DS1287 has died (no suprise there). What
sucks is that even after I run the floppy-based setup
utility, after a reboot (not a power-off cycle), the machine
forgets what I just set, both the data and time, and the
geometry of the A: drive. Seeing as how it thinks there's a
5.25" floppy and it's really a 3.5" high-density drive at
the end of the cable, as you can imagine, it won't reliably
read disks.
So... I have ordered a replacement DS12887 since they no
longer make/ship the DS1287. Couple of interesting app
notes here:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/562
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2681
What I'm wondering is if anyone on the list has ever
replaced a DS1287 with a DS12887. One of the sheets seems
to suggest that I'll need an updated BIOS ROM (clearly not
available for a 286 laptop) to drive the extra stuff
associated with the enhanced century rollover.
Alternatively, has anyone here successfully performed
surgery on a Dallas module? I have disconnected the battery
from a Mostek 48T02 from a SPARC and soldered on an external
Lithium cell, but the packaging makes it easy to get access
to the battery wires coming down from the top (I even put
the battery on a 9V battery snap so it's easier to replace)
I haven't heard of anyone doing this for the more sealed
Dallas modules.
So... anybody else suffer though this?
-ethan
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