I have also found this to be the case. If you send data during
negotiation, the modem hangs up. I've had systems set up to echo data
back to the user at the other end of the modem link. Modem status
messages during connect would hang up the modem. So, in general, don't
send data unless DCD is true OR you are sending commands (like ATDT...).

Harold

On Thu, 18 May 2000 10:27:18 +0200 Steinar Olsen <steinar@NEO.NO> writes:
> Hi,
>
> I use a PIC to communicate with a standard Hayes compatible modem on
> 9600
> baud RS-232.
> The main issue is to call up the system with another modem, get the
> remote modem to pick up the call automaticly, and communicate via
> RS-232 to
> the uProc.
>
> The system works fine, but there is one problem.
> During the time the two modems are communicating after picking up
> the call,
> to set speeds and other initialising before starting the main data
> comunication,
> it will hang up immidiatly if it gets a input on the RS-232 port.
>
> This is a problem on the uProc side
> beacuse the system outputs regulary data on the RS-232, and if this
> output comes before the modem is finished seting up (Online
> indicator lights)
> the modem will hang up.
>
> Yes, there is a number of "no good" sollution to this, like
> stop the dataoutput when reading "RING" at the RS-232, or use the
> "Call indicator" and "online output" to disconnect RS-232 during
> init.. But there must be another way to prevent this from happening.
> Is there something I overlook in the AT command set?
> Why is this happening, is there a meaning behind this function?
> (And no, my datapakages does not contain ATH in the start. ;-) Just
> numbers
> and I have tried with different outputs as well)
>
> Help??
> Anybody??
> :-)
>
>
>
>
>
>
>
>
>
>
>
>
>
> Steinar Olsen
> Electronics Engineer
> ________________________________________________________________
> Norsk Elektro Optikk A/S          Work:   mailto:Steinar@neo.no
>                                   Home:   mailto:Stolsen@c2i.net
> Solheimsveien 62A                 Web:    http://www.neo.no
> P.O. Box 384                      Direct: +47 67 91 11 58
> N-1471 SKAARER                    Phone:  +47 67 97 47 00
> NORWAY                            Fax:    +47 67 97 49 00
> ================================================================

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