From: Spiro Trikaliotis (ml-cbmhackers_at_trikaliotis.net)
Date: 2007-05-15 19:58:11
Hello André,
* On Sun, May 13, 2007 at 10:35:53PM +0200 "André Fachat" wrote:
> I don't have much time, but I have the schematics of the 2031 as the
> 64er magazin claimed it to be, in their IEEE488 interface. See
> http://www.6502.org/users/andre/cbmhw/ieee488/index.html
> if it helps.
Thank you - indeed, it does. I must admit I told others to have a look at
your project before, but when I needed it, I totally forgot it.
Nevertheless, there is still the question w.r.t. the 75161, Pin 11 (DC).
In your schematic, it is not connected. This is exactly the same as in
the schematics in the service manual. Anyway, according to a 75161
datasheet I found on the net (Texas Instruments, SN75161B and SN75162B),
this pin has to be held high or low. I can only think about that the
chip has an internal pull-up or pull-low, so the schematic functions,
nevertheless.
Are you really sure that the schematics on the package is correct?
On a DAMS IEEE 488 interface for the C64 Ruud sent me once, I can
clearly see the pin being connected to something. Unfortunately, the
wire ends somewhere under the 6522, so, I cannot see where exactly it
ends. Additionally, this is the C64 side, which might differ.
Furthermore, in your schematics, I can see you did not use any ferrite
beads, nor condensators for the inputs. So, can I assume they are not
really needed? Are these protections for the inputs, or are they for
EMI?
Regards,
Spiro.
--
Spiro R. Trikaliotis http://opencbm.sf.net/
http://www.trikaliotis.net/ http://www.viceteam.org/
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