reverse engineering: Econet Level 3 fileserver RTC

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station240
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reverse engineering: Econet Level 3 fileserver RTC

Post by station240 » Tue Jul 19, 2011 5:29 am

Continued on from here.
http://www.stardot.org.uk/forums/viewto ... f=8&t=4281

The old black box electronics, its a small plastic tray into which someone has put some electroncs, dangled a cord out one edge, then filled the whole thing with black epoxy. :twisted:

Ok so what's inside ?
Best guess its a 146818 RTC chip, a battery and other bits and pieces.
Reasoning is it would:
a) Fit inside the casing (just).
b) Interface easily with the userport, its 8 bits plus some read/write signals which could be multiplexed.
c) Its common as mud, hence the need to hide it in epoxy.
d) Its included in the later Master 128, and strangely if you use a Master with certain versions of Level3 you don't need the external RTC.

Anyway, all I can get out of it at the moment is the number 223. Which does mean I am reading something at least.

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AndyF
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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by AndyF » Tue Jul 19, 2011 9:43 am

Most versions seem to have it removed from the code from what I've seen. I think it was intended as partly an antipiracy idea and (possibly?) a more accurate* clock

*Its probably no more accurate than the internal B though.

I was under the impression no Master would 'need' it though at all, but perhaps I'm wrong. I used to use 0.92 or 1.07, 0.92 seemed to be the best to me as I could not get some date issues resolved with 1.0.7. Never really had any issues with 0.92 that I recall.

I think they were the versions, although its probably nearly a year since I was near a Level3 server.
Andy

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Adventure games ported across to the BBC (in progress) as soon as I can find some time!

johnkenyon
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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by johnkenyon » Wed Jul 20, 2011 3:56 pm

Ok so what's inside ?
Best guess its a 146818 RTC chip, a battery and other bits and pieces.
My money is on an i2c device like a PCF8583.
I might have to attack one with a Dremel over the weekend...

station240
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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by station240 » Wed Jul 20, 2011 4:21 pm

johnkenyon wrote:
Ok so what's inside ?
Best guess its a 146818 RTC chip, a battery and other bits and pieces.
My money is on an i2c device like a PCF8583.
I might have to attack one with a Dremel over the weekend...
Yes but your not thinking 4th dimensionally.
Did the PCF8583 (or i2c devices in general) exist in 1982 ? Seems the answer is no as the earliest date I could find in the PCF8583 documents is 3rd october 1996.
Page 34 of http://www.nxp.com/documents/data_sheet/PCF8583.pdf

Oh and take care with the Dremel, the idea is to remove the last layer of epoxy with paint stripper. That is leave just enough epoxy to read the part numbers, without disolving the markings on the chips etc. There are guides online to removing epoxy this way.

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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by johnkenyon » Wed Jul 20, 2011 9:25 pm

The heatgun rather than the Dremel is the tool of choice for this job.

From what I've exposed so far, the board contains a single IC in a 16DIP package.
Unfortunately I can't read any markings off the chip, which makes life a bit more difficult.

The connection to the user port is as follows:

PB0 Pin 13
PB1 Pin 11
PB2 Pin 12
PB3 N.C.
PB4 N.C.
PB5 Pin 14
PB6 N.C.
PB7 Pin 15

The 32.768kHz crystal connects to pins 13 and 14.
with what looks like a capacitor between pin 13 and the positive supply.

From my scouting around data sheets I have come to the conclusion that the chip isn't:
146818 - not a 24DIP
MM58174A - Is 16DIP, but the crystal pins don't tally.
CDP68HC68C1 - crystal pins don't tally.

Any more ideas?

station240
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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by station240 » Thu Jul 21, 2011 12:39 am

Not a DS1315, again crystal on different pins.

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BeebMaster
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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by BeebMaster » Thu Jul 21, 2011 12:26 pm

Any chance of some pictures of the insides? Obviously I'm not going to be doing anything similar to my RTC, as it will never function again if I do.

I did conduct some tests using the L3 RTC and all the versions of the L3 code I had at the time, I think with a B and a Master. However, as it was a long time ago and I didn't write anything down or record it, I can't remember what conclusions I drew, if any.

A repeat exercise has now been added to the BeebMaster "to-do" list as item 73, under "Unlock Nexus Hard Disc Sharer".
Image

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Re: reverse engineering: Econet Level 3 fileserver RTC

Post by johnkenyon » Thu Jul 21, 2011 2:14 pm

The results aren't that pretty - the solder side of the board is clear, but the component side is a "tad messy".

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