On Sun, 11 Feb 2007 01:03:22 +0100, Joachim Wunder
put finger to keyboard and composed:
On Sat, 10 Feb 2007 10:27:49 +1100, Franc Zabkar
wrote:
On Fri, 09 Feb 2007 13:37:10 +0100, Joachim Wunder
put finger to keyboard and composed:
might the 16-pin IC a I2C maybe? If so, which
ones were commonly used to control an Intel 8748/8749 ?
I just uploaded seperate larger pics of the front and back side of the
PCB:
front side:
http://img184.imageshack.us/img184/3231/cimg0083kj3.jpg
back side:
http://img187.imageshack.us/img187/1555/cimg0084qg6.jpg
I am sorry to not have done that any earlier. On weekends I now have a
little more time to take better pics and start any systematical
diagnostic tests.
There appear to be 8 or so interconnect pins at the RHS of the 16-pin
IC. Can you trace them to the uC's pins? Do they go to the data bus,
ie pins 12 through 19?
As far as I can see Pins 12, 13 and 14 of the microcontroller are
connected to the interconnect pins at the RHS of the 16-pin IC.
Which pins are power and ground?
Pin 8 is V_SS (GND) and Pin 16 is V_DD (+5V) as far as I measured on
the 16-pin IC.
What is the IC
to the right of the relays?
Thatīs a PHILIPS CNY17-4 Optocoupler.
Which chip/component drives the relay
coils?
Thatīs actually a BC237B transistor each. They are hidden below the
piggyback PCB, unfortunately.
- Franc Zabkar
Thanks
Joachim
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
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