PCB of garage door opener failed: Which PIC is this?

Ack, Jamie. But look at

IMO not a fuse, a jumper.

While the PCB is resting silently in front of me and is connected to

Pin 1: Low , 0.000 kHz, 0.231 V Pin 2: Low , 0.000 kHz, 0.167 V Pin 3: Low , 0.000 kHz, 0.230 V Pin 4: ----, 0.050 kHz, 3.468 V Pin 5: High, 0.000 kHz, 4.979 V Pin 6: High, 0.000 kHz, 4.979 V Pin 7: Low , 0.000 kHz, 0.202 V Pin 8: Vss (GND) Pin 9: Low , 0.000 kHz, 0.204 V Pin 10: High, 0.111 kHz, 4.971 V (frequency slightly alternating around this frequency of 0.111 kHz) Pin 11: Low , 0.000 kHz, 0.012 V Pin 12: Low , 0.000 kHz, 0.012 V Pin 13: ----, 0.000 kHz, 3.335 V Pin 14: High, ?.??? kHz, 4.987 V (frequency randomly alternating from

So, is there anything useful which could be derived from these values? I.e. do these values still tend you to say that it could be a PAL?

Thanks a mil, again Joachim

Well, if you look at the upper left corner on the frontside of the PCB you´ll see nothing that looks any similar to a jumper:

The daughter board is a big red flag that this model has had modifications from the original design. My guess is that there were several variations possible with this circuit board and that still wasn't enough.

I fear that, too. *long sigh*

Anyway, does anybody know which special type of 680 Ohm resistor this red resistor on the upper right corner of the PCB´s frontside is? :

Probably a 1 or 2 W wire wound.

On Sun, 11 Feb 2007 20:51:25 +0100, Joachim Wunder Has Frothed:

Not a fuse.

Hi guys, some drawback today. Oh, well... even the right techie was in today, it´s still not clear whether they have an absolut 100% compatible PCB still in stock for me. They said they need at least 1 day or a few more to find that our for me. All PCBs they currently have in stock (from the shelf, I mean) are equipped with much more modern µC´s. And what I need is an absolute compatible PCB of course.

So, I will keep you posted about the outcome. But this may take some more days. My apologies. But that´s all I have for an update today. Hmm, I think I soon can start opening my own blog about this topic. Oh, well.

Thanks again for all your kind support so far! Joachim

Or one that can be easily hacked to work.

Hi Franc et al,

first of all my apologies for not being able to reply any earlier to this thread with an update. My deepest apologies. Meanwhile I got a spare PCB for the garage door opener which has no need for any piggyback PCB any longer. Thanks God! The 8748 of the old PCB is still alive as well. I was able to access its EPROM contents. Sorry that it took me so long, but getting access to an 8748 adapter for my old ISA EPROM programming card was a real challenge to me. But that´s another story...

Anyway, the new PCB looks very similar to the old one:

front side of the new PCB:

back side of the new PCB:

Franc, you already were so kind as to start to track down the logics of the 16-pin IC a couple of time ago (see text below). I am still stuck in finding out the exact type of this logic IC. And, believe me, I have already looked up hundreds of different datasheets at

Pin 1: Output, controls the basis of the transistor which in turn controls GND of relay no. 3 Pin 2: Output, controls the basis of the transistor which in turn controls GND of relay no. 2 Pin 3: Output, controls the basis of the transistor which in turn controls GND of relay no. 1 Pin 4: Output, controls GND pin of the LED Pin 5: NC Pin 6: NC Pin 7: NC Pin 8: GND Pin 9: NC Pin 10: Input, connected to pin DB2 of 8748 µC Pin 11: Input, connected to pin DB1 of 8748 µC Pin 12: Input, connected to pin DB0 of 8748 µC Pin 13: ? Pin 14: ? Pin 15: connected to GND Pin 16: V_cc (+5V)

I hope you, Franc, and/or anyone else here has a good idea of which logic IC this might be?

Thank you so much in advance. Joachim

I think from today´s day I can answer my question myself: It´s a

TIA, Joachim.

"Joachim Wunder" schreef in bericht news: snipped-for-privacy@4ax.com...

Ever used the old 74S88 in a fast (at the time) control application. The

petrus bitbyter

Yes, Petrus, I am having hell of a problem here in Germany to still find an equivalent to the 74ALS188. No solution yet. On the other hand, I don´t know how critical accesstime is for the 8748 code which is currently stored in the EPROM of the 8748. I guess finding that out wouldn´t be easy without disassembling the code (which I have already done, of course ;) ) and understanding the full code.

So, if anyone here still has any unused 74ALS188 in stock, please let me know and drop me an offer for them. Paying via PayPal preferred. :)

On Tue, 27 Mar 2007 21:26:36 +0200, Joachim Wunder put finger to keyboard and composed:

I have an N82S123 32x8 PROM. It's a 3-state type rather than open collector (N82S23), but I believe that it is otherwise functionally identical. Maybe all that you will need to make it work are pullup resistors ???

Anyway, if it suits your needs you can have it for the cost of postage from Australia. I can also program it for you.

- Franc Zabkar

Thanks, Franc, for your kind offer. I guess I have just found a good source in Germany for 74S188 from National. Hmmm, I am still curious of which programmer you actually have. And, can any programmer even copy an existing 74ALS188 if it (the programmer) can program an unused

Joachim

On Tue, 27 Mar 2007 23:28:43 +0200, Joachim Wunder put finger to keyboard and composed:

I have an old Sunshine Expro-60.

AFAIK these PROMS have no security bits so you should be able to read their contents without any trouble. The 74S188 uses fusible link technology which means it would require a different programming algorithm than an EPROM, but accessing its data should be no different.

BTW, what good is a device programmer that is unable to verify (ie read and compare) the device it has just programmed? ;-)

- Franc Zabkar

Ah, ok. Don´t know this device, but must be powerful.

Yes, the same applied to my two 8748 (one on the old PCB and one on the new PCB): No security bits, so I was able to read them out, finally. ;) Thanks God. The source codes (they slightly differ from each other) both show a couple of the following opcodes:

movx a,@r1 movx @r1,a movx a,@r0 movx @r0,a

That first confused me a little, ´cause these movx commands normally reference external memory, but \RD and \WR pins of my 8748 are not connected to anything on the PCB. Hmmmm, strange, isn´t it? The

outl bus,a ins a,bus

commands seem obvious to me. Hmmm. Well, anyway, I am very satisfied that the 8748´s EPROM content was readable at all. :)

OK. Sounds fine. Meanwhile I even google´d enough to know now more about the programming algorithms for PROMs in general.

That´s absolutely right. ACK.

Kind regards, Joachim