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

J

Joachim Wunder

I think you're right about the uC being an 8748 or 8749. I'd confirm
that the reset pin (4) is not being held low by a shorted reset cap,
especially if it is a tantalum type. BTW, pin 5 is connected to Vcc,
so the 10K resistor is essentially a pullup.
Click to expand...

Ok, I just measured the 8748/49 again with my logic tester:

Pin 4: HIGH, 0.000 kHz, 4,977 V

Pin 5: HIGH, starting with around 700.000 kHz and then steadily
dropping down to 0.439kHz, 4.987 V

I hope this is a good sign for the µC?
I have an old (1991?) Sunshine Expro-60 with an ISA controller card in
an old 486 box.
Click to expand...

Yes, we enthusiasts never throw away these good old pieces of h/w
since we know that some day we´ll definitely need it again. :)
That's a big surprise. I would have thought these dishes were cheaper
in Europe where satellite TV is much more widespread.
Click to expand...

Well, the last mesh dish which I could get in Europe was a KTI CKD-12
12 feet dish 2 years ago. And this was by far more than by accident!
Hehe. But when it comes to C-band feedhorns, LNBs and that stuff,
there is almost no way to get anyone in Germany who is willing to
import that for you. No way. Now, I have assembled the 12 ft mesh dish
already, I am still investigating for a valid dual-axis-mount which is
capable to withstand high windloads. And this topic is a real
nightmare, believe me. But I don´t want to get any more offtopic here.
Oh man...

Kind regards,
Joachim
 
J

Joachim Wunder

AFAICT, the 16-pin IC, if the piggyback PCB faithfully mimics the
pinout, has at least three outputs at pins 1,2,3, each of which drives
the base of a relay driver transistor. Each pin has a pullup resistor
to Vcc, so I suspect that the outputs may be open collector.

Since pins 10,11,12,13 of the IC are connected to the uC's data bus, I
suspect that they may be inputs. If so, then I believe that these
inputs would need to be latched. The fact that there is a "VOH" on the
body of the chip suggests that it might be programmed, in which case
it could be a PAL.

- Franc Zabkar
Click to expand...

While the PCB is resting silently in front of me and is connected to
+12V (and to +5V via a voltage regulator on the PCB) the 16-pin IC
shows up with the following readings (directly measure on the IC´s
pins):

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
0.000 kHz to more than 2 MHz)
Pin 15: Low , 0.000 kHz, 0.000 V
Pin 16: High, 0.000 kHz, 4.984 V

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
 
H

Homer J Simpson

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:
http://img184.imageshack.us/img184/3231/cimg0083kj3.jpg .Only a few
drilled small holes. But anyway, there is nothing which could have
protected the circuitry of the PCB on the (N)eutral side of power
supply (230V AC). Nice manufacturer, I know...
Click to expand...

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.
 
J

Joachim Wunder

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.
Click to expand...

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? :
http://img184.imageshack.us/img184/3231/cimg0083kj3.jpg
 
J

Joachim Wunder

No, I didn´t tried them yet. But I have done some good progress today:
After a whole bunch of further phone calls I was now finally able to
find out the manufacturer of the PCB. It´s a very small company in
Saar/Northern Germany. They are not on the Web, so you simply can´t
find them there, unfortunately. But the company who installed the
garage door opener back in 1990 had a deeper look into their archive
to find out this small company for me, again. Thanks God. Well, even
this company is located in Northern Germany but not presented on the
Web at all. So, life sometimes really sucks, I know.

Well, unfortunately, the techie himself who designed the PCB wasn´t in
today, but another tech person of the same company told me that they
MIGHT have some spare PCB still in stock. Thanks God. But this is only
an assumption and cannot be clarified before the upcoming Monday. So,
I will keep you all posted here. :) And, moreover, the techie whom I
had on the phone today even told me that all employees are definitely
not authorized to hand out any circuitry plans or specs/types of the
microcontroller and the accompanying IC. Holy cow.... anyway...
there´s some hope the next Monday. I´ll report back and keep you all
posted with an update then.
Click to expand...

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
 
J

Joachim Wunder

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:
http://img143.imageshack.us/img143/1120/cimg0131kd8.jpg

back side of the new PCB:
http://img68.imageshack.us/img68/4202/cimg0128ms3.jpg

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
www.datasheetarchive.com. Hmpf. The manufacturer of the PCB is still
not able (or should I better say willing...) to reveal the exact type
of this IC. But they told me that it´s definitely no PAL. What is
known to me is the following pin assignment:

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
 
J

Joachim Wunder

I think from today´s day I can answer my question myself: It´s a
74ALS188 according to the PCB´s manufacturer. Does anyone know where
to still get such ancient PROMs and where to get an affordable
programmer for it as well?

TIA,
Joachim.
 
P

petrus bitbyter

Joachim Wunder said:
I think from today´s day I can answer my question myself: It´s a
74ALS188 according to the PCB´s manufacturer. Does anyone know where
to still get such ancient PROMs and where to get an affordable
programmer for it as well?

TIA,
Joachim.
Click to expand...

Ever used the old 74S88 in a fast (at the time) control application. The
74ALS188 is one of the same family of 32x8 bit PROMS. I've only the pinout,
no datasheet anymore. Even in the old days the device was hard to find. If
you can find them now, I guess they will have a price...
But once you know the contents, you can program it's logical function in
another device like a PAL. Which will be the function of the piggyback on
the old PCB. You may be able to use an EPROM or an EEPROM as well. I
remember those "fast" 74S88 had an accesstime of 50ns. Modern (E)EPROMS are
faster.

petrus bitbyter
 
J

Joachim Wunder

Ever used the old 74S88 in a fast (at the time) control application. The
74ALS188 is one of the same family of 32x8 bit PROMS. I've only the pinout,
no datasheet anymore. Even in the old days the device was hard to find. If
you can find them now, I guess they will have a price...
But once you know the contents, you can program it's logical function in
another device like a PAL. Which will be the function of the piggyback on
the old PCB. You may be able to use an EPROM or an EEPROM as well. I
remember those "fast" 74S88 had an accesstime of 50ns. Modern (E)EPROMS are
faster.

petrus bitbyter
Click to expand...

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. :)
 
F

Franc Zabkar

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. :)
Click to expand...

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
 
J

Joachim Wunder

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
Click to expand...

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
74ALS188? Please pardon my stupidity, but except programming EPROMs
and 8748 I never did any 'acrobatics' with PROMs...

Joachim
 
F

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.
Click to expand...

I have an old Sunshine Expro-60.
And, can any programmer even
copy an existing 74ALS188 if it (the programmer) can program an unused
74ALS188? Please pardon my stupidity, but except programming EPROMs
and 8748 I never did any 'acrobatics' with PROMs...

Joachim
Click to expand...

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
 
J

Joachim Wunder

I have an old Sunshine Expro-60.
Click to expand...

Ah, ok. Don´t know this device, but must be powerful.
AFAIK these PROMS have no security bits so you should be able to read
their contents without any trouble. The 74S188 uses fusible link
Click to expand...

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
74ALS188 is connected to port P0 (i.e. the BUS) of the 8748. So, 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. :)
technology which means it would require a different programming
algorithm than an EPROM, but accessing its data should be no
different.
Click to expand...

OK. Sounds fine. Meanwhile I even google´d enough to know now more
about the programming algorithms for PROMs in general.
BTW, what good is a device programmer that is unable to verify (ie
read and compare) the device it has just programmed? ;-)
Click to expand...

That´s absolutely right. ACK.

Kind regards,
Joachim
 
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