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PICList Thread
'Modems'
1999\04\08@181032 by johnb

picon face
I just returned to the PIC-LIST after a long absence. It seems to be
suffering from some kind of disaster that gives over 120 messages per
day, of which only a dozen contain PIC-related topics. I hope it gets
better.

Somebody once wanted a Modem chip that would interface easily to a PIC.
The perfect device may be at:
http://www.cmlmicro.co.uk
The company is called Consumer Microcircuits Limited (CML) and there is
also a
US Web site.

The devices are the CMX624 (V23/Bell 202) and CMX644 (V22/Bell212a).
They seem ideal because:

Both contain a UART
The UART needs 3.686MHz or 7.3728MHz, which could also be the PIC clock
The interface is serial (SPI/Microwire compatible), which is 4 pins (+
optional IRQ pin)
Has a DTMF dialler, ring detector, data scrambler, loopback test, etc
Runs on 3 to 5 volts, 2 milli-amps
Has 1 micro-amp standby current (the ring detector still works in
standby)
24-pin SOIC/SSOP/DIL package

It only needs an active hybrid and isolating transformer to complete the
modem. And - er - approval for use. But I have a feeling that a company
called (I think) Cybertek make exactly that part.

I haven't used this chip; I only have the data sheet. I have no idea of
the price. The CML site has updated Data Sheets, Ev-kits, etc.


John Blackburn,
London UK.

1999\04\08@201500 by Barry King

flavicon
face
> It only needs an active hybrid and isolating transformer to complete the
> modem. And - er - approval for use. But I have a feeling that a company
> called (I think) Cybertek make exactly that part.

I think you mean Cermetek.  The "Hybid and Isolation" component is
called a DAA (for data access arrangement).  It takes the audio
signals and connects them to the line with pre-engineered
protection for the device and the phone line.

Some of the Cermetek DAAs are approved so that a product which
uses them properly is automatically approved by FCC for sale in the
US.  Also for DOC in Canada, IIRC.  They also have models which
satisfy the slightly different and always "strictly needed" variants
for various EU countries.

<editorial>
I almost wish the EU would harmonize Telecom approvals, but its
likely to result in "all of the above" levels of complexity (and
therefore cost), like the other approval harmonizations have.
</editorial>

Cermetek also makes packaged modems which take Asynch serial at TTL
levels (like from PIC Asynch pins) directly, including the DAA, as a
hybrid module.

Cermetak has a WWW site, but I don't have the URL.  Also, there is
another maker of these things, whose name escapes me, but a search
for "DAA" on altavista will likely turn them both up.

Hopefully, this helps.

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
spam_OUTbarryTakeThisOuTspamnrgsystems.com
"The witty saying has been deleted due to limited EPROM space"

1999\04\09@023033 by Dr. Imre Bartfai

flavicon
face
Hi,
it was me who asked for a modem chip concerning the thread "secretify [I
do not know whether the wording exists ;-) ] phone conversation". Thank
you for the advice.
Imre


On Thu, 8 Apr 1999, John Blackburn wrote:

{Quote hidden}

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