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Tl Posts:

Posted - 2/15/2005 6:16:03 AM  Show Profile  Email Poster  Edit Message
i'm new here and am doing a project which requires connecting two modems with a telephone line and synchronising communication between them and i have to use external modems.i have been trying for 2 weeks without success.
i have the following
1)GVC 56k modem (taiwan)-rcv.56BPF (which somebody told me was a rockwellchipset).it looks like this.

now i guess need to configure the s-registers. i couldnt find the users manual nor info about what each of these s-registers mean and what values they take
would immensely appreciate if someone could help with the manual .i tried reaching their home sites but in vain. any info about the above case would be helpful too


Tl Posts:

Posted - 2/16/2005 2:33:47 PM  Show Profile  Email Poster  Edit Message  v.Richards Homepage
Start with both modems at factory defaults -

The 56k modem needs to have 56k disabled -
for Rockwell modems - see

One modem should be set to autoanswer -

So long as both modems are in use by suitable communications program, dialing should result in autoanswer & datacomm.

Aloha! Richard.

Tl Posts:

Posted - 2/18/2005 9:29:42 AM  Show Profile  Email Poster  Edit Message
the outputs upon using the ATI* command on both the modems were as follows.
GVC 56K - RCV56DPF_PLL L8571A Rev_19.00/19.00
boca - V2.050C_V34_ACF_DS1
i tried searching over the net with my conditioned searching skills but could find neither user manual . can someone help me find it! i'm in desperate hurry!
and the "at +ms=.." didnt work. must probably be cos of the change hcf acf thing
thanks - a - lot
Tl Posts:

Posted - 2/18/2005 11:37:01 AM  Show Profile  Email Poster  Edit Message
Both modems use the Rockwell versions of the ACF chipset.

GVC Model: 1156V/R21D
Rockwell ACF 56K (2 Meg ROM)

Generic AT command manual;

Here is whats left of GVC support;

Here is whats left of BOCA support. File Area 14 is modems. look for ATCOMM.DOC.
Zoltrix made many modems using ACF chipset and have much information under their support section.

Tl Posts:

Posted - 2/23/2005 9:18:11 AM  Show Profile  Email Poster  Edit Message
thanks-a-lot! it worked perfect .
an ill written paper on the project refers to something about synchronising the two modems . how does one do that?
Tl Posts:

Posted - 2/23/2005 10:51:10 PM  Show Profile  Email Poster  Edit Message
Without seeing the information "synchronizing the two modems" in context I am not sure what the author meant by this statement.
Tl Posts:

Posted - 2/25/2005 9:20:35 AM  Show Profile  Email Poster  Edit Message
ok , now the project involves remotely monitoring an s7-200 plc through 2 dial up modems . now s7-200 1) needs to have compression , dtr and flow control disabled and 2) connect at 9600bps . now its a lot tougher than it sounds cos i'm havin hell of a time trouble shooting mistakes and will have to work on hit -n-trial.
in this case how do u synchronise

also i'm tryin out these modems and as usual manuals are hard to come by . please help
1)D-link DFM-560E 56kbps
2)GVC 33600bps V.34 ASVD

i really appreciate this response

Tl Posts:

Posted - 2/27/2005 9:03:45 AM  Show Profile  Email Poster  Edit Message
hi again!
1)it was talkin about an option called "synchronise remote modem" in the control panel of windows.i couldnt find one of those options in XP . would someone know about it in anyother version of windows.

2)d-link : RCV56DPF-PLL L8571A Rev 33.00/33.00
gvc : RCV336DPFSP Rev 44BC
now i have two manuals one says
which one am i supposed to use and for which modem . if i may have to use anyother manual please refer to it.


Tl Posts:

Posted - 2/28/2005 5:31:39 AM  Show Profile  Email Poster  Edit Message
You need help from an active online community of people working in Industrial Automation,
"the global online community of automation professionals"
"Check out the technical articles and participate in the technical discussions."

If you don't already have the manual for the Siemens PLC you can download it from Siemens;
The PLC should have come with some version of the Siemens STEP 7-Micro/WIN software. You can also download the latest updates and patches for the software from the Siemens web site. There is information in the manual on configuring modems using the modems "default" settings with this PLC. There is also information on configuring the RS-232 PPI Multi-Master cable (RS-485 to RS-232 adapter) if this is what your using or if you decide to use the optional EM-241 modem modual.

" needs to have compression , dtr and flow control disabled and 2) connect at 9600bps ."
If all your doing is monitoring the PLC with a remote dialup modem I am not sure why the above is required. These modems will work using their default settings and the Micro/WIN software for monitoring the PLC.

If this is a learning, teaching (school) project the restrictions are understandable.

* "synchronize remote modem"
I believe the author is referring to Synchronous vs Asynchronous Data Transfer.
In the case of the the SIEMENS PLC the Siemens provided software might provide a way of monitoring if the remote is in fact synchronized with the PLCs RTC
(Real Time Clock).

"Synchronous vs Asynchronous Data Transfer"
"In order for the stream to be sent, synchronous modems must be in perfect synchronization with each other. They accomplish this by sending special characters, called synchronization, or syn, characters. When the clocks of each modem are in synchronization, the data stream is sent."
"Timing refers to how the receiving system knows that it received the start and end of a group of bits. Two major timing schemes are used: Asynchronous and Synchronous Transmission."
"This Start Frame is used to tell the receiving station that a new packet of characters is arriving, and it synchronizes the receiving station's internal clock."

All the modems you have listed appear to use versions of the Rockwell ACF chipset. The Generic AT command manual should work for all of them. The basic AT commands did not change as new protocols were added (V.34, V.90, V.92). Commands specific to the newer protocols (V.90, V.92) should be noted as such.

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