RE: TI-H: RE: Link com voltages


[Prev][Next][Index][Thread]

RE: TI-H: RE: Link com voltages



Thanks for the info. I noticed that several people were having trouble with
transistor amps for sound so I thought I would design a single op amp and
give it to the poor souls :-)

-----Original Message-----
From:	Mel Tsai [SMTP:tsaimelv@pilot.msu.edu]
Sent:	Thursday, September 18, 1997 5:24 PM
To:	ti-hardware@lists.ticalc.org
Subject:	Re: TI-H: RE: Link com voltages

>On Mon, 15 Sep 1997, Jan Zumwalt wrote:
>
>> Could someone please tell me what the link voltages are during
>> communication?  I know it uses reverse logic but what are the voltages,
>> 0v and 5v, or 0v and 3v, etc? 
>
>The calculator's link voltage depends on the batteries. If the batteries
>were new, the voltage would be slightly higher. The voltage is likely to
>be near, but less than, 5v. If you wanted to feed a 5v signal into the
>link port, that would not be a problem. Unless you had the link port set
>at 0v at the time.. If you're trying to attach something like 74xx
>logic/glue to the link port, it should work.


Actually the linkport voltage varies directly with the output
resistance.  The higher the current the linkport is outputting, the
lower the output voltage.  At about 0.5ma current draw, the output
voltage is zero.  At zero current draw, the linkport voltage is about
5.2 to 5.3 volts (this can only be tested with high accuracy
multimeters, however, because cheap ones will draw current and it will
seemingly be outputting 4.9 or 4.8 volts).  So the output voltage of
the linkport can (and will) swing between 0 and 5.3 volts, and with
TTL loads it will probably be between 3 and 4 volts for logic 1.

-Mel
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The TI-Memory Expansion Homepage
-http://www.egr.msu.edu/~tsaimelv/expander.htm
Warning
Could not process part with given Content-Type: application/ms-tnef