SAIA with SCADA via modem


Thread Starter

Nuno Ventura


I need some help urgently. I hope you can help me.
I need to comunicate from Citect (SCADA) via PSTN with a SAIA PCD2 PLC. For that I have 2 Multitech MT2834ZDXIe modems.

In the PLC side:

I'm using a MultiTech MT2834ZDXIe 33.6Kbps modem connected to serial RS232 interface n.1 in SAIA PCD2 (using Tx, Rx, CTS, RTS, GND, DSR, DTR and DCD signals) The interface is configured in "SBUS Slave" and "Data" mode in PG5 programming software, with FBox from Fupla editor, the connection with modem is configured to be 9600bps and 8-N-1. The modem inicialization string in the Modmbase.dat file is "ATE0M0&E0&E14&E3&Q1<CR>.

In the PLC program I have the follow Fbox's:
- Modem 8, it's the modem driver fbox
- Call Master Fbox, it's used to define the parameters for making calls to a Master station
- Incoming Call Fbox, it's used to detect and handle incoming calls

In the Citect (PC) side:

Windows 2000 Service Pack 2
Citect 5.40 Version 5.40 Rev.00 Service Pack C

The Citect SBUS Driver is V3.00.01.001.
I use SBUS protocol in data mode: citect.ini with "[SBUS]SendBreak=2".(for DataMode)

Boards: Board type COMX, Adress 0

Ports: Port Number -1
Boud Rate 9600
Stop bits 1
Data bits 8
Parity None

I/O Devices: Address 0
Protocol SBUS
Phone Number 244XXXXXX
Caller ID PCD2_S

Modems: Name "Standard 33600 bps Modem"(the same as in Control Panel)
Outgoing Calls TRUE
Incoming Calls TRUE

In the Control Panel the modem is defined with:
Maximum Port Speed 9600
Extra Initialization commands ATE0V1Q0M0&E0&E14&E3&Q0

I also tried to put this initialization string in the Ports form, Special opt field with -iATE0.... and some variants of this string.

With this, I can make calls and answer calls, but after the connection established and Carrier Detect led between both modems lights up, the
IOdevice goes on-line for an instant and the connection hang's up.

With the same inicialization string, and with modem configured for remote Programming with SBus PGU mode, the communication with the laptop running the Programming software run's ok, so I suppose that the PLC side inicialization string can be the same and that's correct !!.

Any sugestions will be apreciated.


Nuno Ventura, Eng.
Dep. Automacio e Sistemas
EST - Empresa Servios Tecnicos, Lda
Rua da Granja, N=BA10 B - Boa Vista
Apartado 803
2401-978 Leiria - Portugal

Tel: +351 244 850900
Mov.+351 96 6974507
Fax: +351 244 851974
[email protected]