Searching \ for 'Using a PC modem with a PIC' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: techref.massmind.org/techref/microchip/devices.htm?key=pic
Search entire site for: 'Using a PC modem with a PIC'.

Truncated match.
PICList Thread
'Using a PC modem with a PIC'
1998\06\25@163724 by Gary T. Pepper

flavicon
face
Hello Everyone,

After reading the thread about using a 16c64 to dial a modem and link to a
PC, I've thought of a variation to this question:

Since PC-based modems are relatively cheap and plentiful these days, has
anyone tried to take an off-the-shelf PC-based modem card (e.g. ISA based)
and interface it directly to any PIC processor?  This might be an easy (and
cheap) method of getting PIC-based modem communications going.  Of course,
one could also use an external modem that communicates via an RS232 link,
however, an ISA-based modem card soution is likely cheaper.  Any comments?

Regards,
Gary Pepper

Ottawa, Ontario, Canada
e-mail: spam_OUTgpepperTakeThisOuTspamcapitalnet.com

1998\06\25@194206 by Harrison Cooper

flavicon
face
               Or better yet, a PCI based interface?  Altera and Xilinx
both offer PCI cores for their FPGA's

               I'd be interested in at least the ISA interface, figure
its just basically a parallel dump of data and control for reads and
writes.

                               ----------
                               From:  Gary T. Pepper
[SMTP:.....gpepperKILLspamspam@spam@CAPITALNET.COM]
                               Sent:  Thursday, June 25, 1998 2:10 PM
                               To:  PICLISTspamKILLspamMITVMA.MIT.EDU
                               Subject:  Using a PC modem with a PIC

                       Hello Everyone,

                       After reading the thread about using a 16c64 to
dial a modem and link to a
                       PC, I've thought of a variation to this
question:

                       Since PC-based modems are relatively cheap and
plentiful these days, has
                       anyone tried to take an off-the-shelf PC-based
modem card (e.g. ISA based)
                       and interface it directly to any PIC processor?
This might be an easy (and
                       cheap) method of getting PIC-based modem
communications going.  Of course,
                       one could also use an external modem that
communicates via an RS232 link,
                       however, an ISA-based modem card soution is
likely cheaper.  Any comments?

                       Regards,
                       Gary Pepper

                       Ottawa, Ontario, Canada
                       e-mail: .....gpepperKILLspamspam.....capitalnet.com

1998\06\25@204430 by Jerry Meng

flavicon
face
Hi Gray,

If you connect PIC direct to a ISA based modem, at least 8bit port(data)
should be used, more you also have to supply the address line, W/R, etc,
like controlling a intel8250, it's too complex, I think.

I guess the ISA modem also has a UART, if you can find it, can still use
a SCI port to driven it. I don't know if the ISA modem is supplied via
+12 or -12 from ISA bus, if so, your PIC power supply must output
those voltage.


Jerry

At 04:10 PM 6/25/98 -0400, you wrote:
{Quote hidden}

1998\06\25@224404 by Mike Keitz

picon face
On Thu, 25 Jun 1998 17:01:27 -0600 Harrison Cooper <hcooperspamspam_OUTES.COM>
writes:

>                I'd be interested in at least the ISA interface,
>figure
>its just basically a parallel dump of data and control for reads and
>writes.

Hooking up an ISA modem to a PIC system would be real simple.  You'd just
need an 8-bit parallel interface to the 8 registers in the 16550 chip.
So 8 data pins, 3 address pins, a read strobe and a write strobe.  It
should be OK to tie the other address pins to 3Fx and set the modem for
COM1.  And it may be useful to use the interrupt feature.  I don't think
you need any clocks to a modem card, though some may need +-12V for the
analog circuitry.

_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]

1998\06\26@180201 by paulb

flavicon
face
Harrison Cooper wrote:

> I'd be interested in at least the ISA interface, figure its just
> basically a parallel dump of data and control for reads and writes.

 That's about it.  I was about to interject that there is an IRQ system
too, but I daresay you don't have to use it, especially if the thing
*thinks* it's a 16550.

Jerry Meng wrote:

> If you connect PIC direct to a ISA based modem, at least 8bit port
> (data) should be used, more you also have to supply the address line,
> W/R, etc, like controlling a intel 8250, it's too complex, I think.

 Not *too* complex overall, one should hope.  How much simpler could
you really expect?  A serial interface is hardly simpler when you waste
an awful lot of instruction cycles in the serial routines.  OTOH, if you
used some sort of serialiser, it would probably help to use the IRQ as
well.

> I guess the ISA modem also has a UART, if you can find it, can still
> use a SCI port to driven it.

 Ahh!  There's the trick!  It does *not*.  It imitates one to a trivial
extent.  You've never wondered why an internal modem can be set for
*any* baudrate and still works at top speed?  It just ignores the
baudrate registers and latches the parallel data into/ out of the local
processor.  Makes it very easy to emulate a 16550 or 16560 buffer set.

> I don't know if the ISA modem is supplied via +12 or -12 from ISA bus,
> if so, your PIC power supply must output those voltage.

 Dunno.  I suspect *not*, particularly the modern ones.  Look at the
board for the thicker traces.  Gnd and 5V are two at each end and should
have a tantalum between them at each end.  If there are more than one
thick one in between, or more tantalums, then yes, it does require the
+/- 12V.

 Cheers,
       Paul B.

1998\06\26@205137 by Harrison Cooper

flavicon
face
                       Jerry Meng wrote:

                       > If you connect PIC direct to a ISA based
modem, at least 8bit port
                       > (data) should be used, more you also have to
supply the address line,
*       W/R, etc, like controlling a intel 8250, it's too complex, I
think.

                       No, I did 8250 interfacing with a Z80 in
assembly.  Just load the chip with the init data, I hope we all
                       Are capable of doing that.

                                 Not *too* complex overall, one should
hope.  How much simpler could
                               you really expect?  A serial interface
is hardly simpler when you waste
                               an awful lot of instruction cycles in
the serial routines.  OTOH, if you
                               used some sort of serialiser, it would
probably help to use the IRQ as
                               well.

                               > I guess the ISA modem also has a UART,
if you can find it, can still
                               > use a SCI port to driven it.

                                 Ahh!  There's the trick!  It does
*not*.  It imitates one to a trivial
                               extent.  You've never wondered why an
internal modem can be set for
                               *any* baudrate and still works at top
speed?  It just ignores the
                               baudrate registers and latches the
parallel data into/ out of the local
                               processor.  Makes it very easy to
emulate a 16550 or 16560 buffer set.

                               > I don't know if the ISA modem is
supplied via +12 or -12 from ISA bus,
*       if so, your PIC power supply must output those voltage.


               I think the +/- 12 is only when driving out for RS-232.
Could be wrong but looking at modem card, what is there
               That would need this? Its all TTL or CMOS parts and
ASIC's.  Most likey would be running on 3.3V anyway

                         Dunno.  I suspect *not*, particularly the
modern ones.  Look at the
                       board for the thicker traces.  Gnd and 5V are
two at each end and should
                       have a tantalum between them at each end.  If
there are more than one
                       thick one in between, or more tantalums, then
yes, it does require the
                       +/- 12V.

                         Cheers,
                               Paul B.

                       If I remember, I'll talk to a friend who used to
be at 3COM (US Robotics....was Megahertz) who was working
                       On modem cards, see if he has any specs or such.
He isn't there anymore, but probably remembers.  A lot of what
                       Is done on the cards is addressing space and IRQ
setups, which wouldn't be needed in a standalone hardwired application.
                       The advantage of using an off the shelf card
remains that you don't have to redesign the telco interface stuff and
worry about
                       Approval.  And designing at higher speeds is
also fun.  Doing a 125 MHz circuit as we speak...write...read...

More... (looser matching)
- Last day of these posts
- In 1998 , 1999 only
- Today
- New search...