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ZETNET-ATARIANS DATA FILES (18) Computer Internals
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Falcon Clock Chip:-
Falcon owners should be familiar with the fact that at some point in
time their real time clock will cease to function. You will no longer
have access to your talking clock,neither will your files become stamped
with the time and date that you wrote them.Very annoying if you ever
need to locate files by using the 'sort by date' function from the
desktop.
The reason for this is that the tiny lithium battery in the clock IC has
reached the end of it's life, which is somewhere between 5 and 10 years.
Falcon owners with the original clock chip are now living on borrowed
time. One indication is that your clock becomes slower and slower and
you start having to reset the time at weekly intervals.
Two solutions , but you need to be confident in stripping down your
Falcon without causing any damage,and some delicate soldering is also
required for either option :-
(1) Replace the clock chip.At present the MCCS146818BM is availiable from
Dial Electronics Ltd., (see section 3 for contact details).
(2) Leave the original chip in place. Use a sharp knife to cut through
the soft plastic top of the chip. Be careful ! The crystal is situated
at the lefthand end of the chip (the same end as the little dot marked
on the chip casing),and you don't want to cut through the crystal
connections by mistake.The knife only needs to penetrate about 1mm
into the casing. ( Left and right, is as if looking at your Falcon normally,
keyboard being nearest to you.)
Once you have cut a trapdoor into the top of the chip casing,use tweezers
and gently pick away the rubbery filling until you reveal the small
battery sitting on top of the IC chip. There is no need to attempt to
remove the old battery.You will see the two vertical contacts to which the
battery connects to the IC chip.The lefthand side one is +ve,the righthand
side one is -ve.Gently clean up these contacts. Cut through the lefthand one
using a fine file or better still a small engraving tool, at a point midway
between the battery and the upright connection.
With a soldering iron and pair of tweezers you may now remove the portion
of the battery tag remaining on the upright left hand connector. The
old battery is now well and truly disconnected.
All you have to do now is to solder two leads (about 3" in length) to each
of the upright contacts. Obtain a suitable 3 volt Lithium battery,such as a
CR2032, and you will also need a coin cell holder since one should not
attempt to solder directly to a button cell. Solder the leads that you have
already installed on the chip to the coin cell holder.
All done ! Except for finding a suitable place to stick the battery
holder to the motherboard.Don't try and place it too near the chip as
there will be insufficient room to replace the metal work when you
start to reassemble your Falcon.Find a suitable area slightly towards
the rear of the machine. I used a stickpad to secure the battery to
the motherboard.
Lastly do check the polarity before inserting your battery into it's
holder.Positive (flat side of the battery) goes to the left hand connection
on the chip. Ensure that no exposed metal parts of the battery holder can
come in contact with any other components on the motherboard or you might
have disasterous results. Mask off if necessary. Avoid the temptation to
glue the battery holder to the top of any of the adjacent computer chips
as this could cause the chips to overheat.
I have seen some postings that an alternative to the MCCS146818BM is
the DS1287 (Dallas/Maxim), possibly also the Symphony SL1287 as used
in older PCs. Both of these chips are of solid encapsulation, and the
internal battery and it's connections can only be accessed by carefully
cutting down into the chip using a dental burr. I have tried this with the
DS1287, and it is possible to do if you have the tools and patience.
Your best bet is to get a MCCS146818BM while they are still around.Make
sure that you do not get sold a MCCS146818AFN as that is a totally
different beasty. Current price for the MCCS146818BM is 250p excluding
vat and post in the UK.
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no volitie backed up and
non volitile perishable
i design chips in code c++
and sometimes non volitile means 50000 write + ~ {around about !}
where the chip maker just guarantees a certain amount of flashes
of the nvram before it will definlaty fail ! battery backup or not !!!
check out my web sites i write code that builds in these fails
for some major electronics sims like proteus vsm
Hey, PROTOS, I don't get it.
In the pictures, it doesn't seem to be any cutting on the chip, but a soldering directly to the pins of the IC. Is that right?
this would mean that you can leave the old battery in place without even disconnecting it. It would be great. I would just need to know the pin numbers where to solder the battery
Can you shed some light?
Thanks.
By the way: great job in finding this stuff and STICKYing it. I already roamed two or three times in the forums to find it and then didn't have the time to do the mod, and I had to search again, and I didn't have the time again, and so on.
Now it will be easier
if you go to the Dallas Semiconductor / Maxxim website, you can sign up (free) and get some engineering/protyping samples of the Dallas clock chip. It costs you nothing and now I have two spares sitting at home all the way from Dusseldorf no less!
( For those looking in, System C is the half arsed language that tried to merge hardware design and software design languages together "I know lets take a sequential language and use it to describe something that is infinitely parallel!" )
I design chips in VHDL & Verilog and have done for... oh crap 7 years (getting old!)
I just soldered a socket on the motherboard on which i plug a DS12887A+ (that i got from Maxim-Dallas as a sample, thanks to them).
Everything looks to work now: I set
* the language on French
* the keyboard on German
* color to 16
* résolution to 640x480
and these settings are now kept when I reboot!!
But i do not know how to set the date and time. BootConf does not offer the possibility to set such date and time. What is the program I can use to set the date/time?
Thanks
EDIT: xControl did the job... Now, the clock remains after shutdown/reboot.
François
Last edited by brainois on Sun Jun 11, 2006 4:38 pm, edited 1 time in total.
To set the time and date you can use a. Control panel b. Clocky c. Tlkclock and probably a lot of other programs. I am envious. I would destroy my motherboard if I tried to change the chip so no time for me.
This was the first time I soldered something... Yesterday, I bought the materials for €13... If you take care, it is really possible. And it is unlikely to damage sth as the area where the chip sits, is not "crowded" There are onlt three of four pins where you must be more carefull.
First, register with Maxxim and get an account. Then, so a search for the DS12887A. Somewhere on that page you can 'order', you can 'order' up to two 'samples' that you can use for engineering/prototyping purposes.
Note: Only some chips are 'free samples'.
If anyone is really stuck, send me a pm with your maxxim username/login and the address you want the chips sent to.
What lovely people at Matrixx, they sent me the sample so I can now replace my RTC. Rather brilliant of them aswell. I used the company name that I occassionally trade under that is clearly found on the internet as a web design company so they must have known that they were for personal use!
As for the A version, I think the A means that the NVRAM can be flashed clear, in the spec sheet it says:
RAM Clear Function (DS12885, DS12887A, and DS12C887A)
So I'm assuming the non A version needs to be cleared another way. Seems weird though, but would be used in situations where you don't want the NVRAM getting wiped.
(getting old!)
