About Modems

Unitronics' controllers can be hooked up to PSTN (landline), or GSM/GPRS modems via the RS232 COM port. Unitronics provides kits that comprise modems that have been tested by Unitronics and are supported for use with Vision, Jazz, and M90/91 PLCs.

Before you can use modems in your application, you must use Modem Services to initialize both the PC and PLC-side modems.

This process is referred to as 'Prepare Modem'.

Modem services

Modem Services is located on the Connections menu.

To use Modem Services, connect the modem to a PC, using the cable supplied by the modem manufacturer. You can then initialize the modem.

Once you have connected initialized modems to your PC and PLC, you can use Modem Services to establish communications with a remote PLC.

PC-side Modems

You can use a PC modem to access a remote, modem-linked controller and perform any task, just as you would if the PLC were directly connected to your PC. For example, you can

Dial a remote PLC modem and receive calls from a PLC.
Download, upload, and edit the controller program via the modem connection.
Run Online test mode.
Download an OS to the controller via modem.
Use OnLine test and Information Mode to troubleshoot problems in remote controllers and applications.
Read and write data to/from controllers via Remote Access or Unitronics' communication .dll utilities.
Receive and send SMS messages via SMS options.

PLC-side modems

Via modem, a Vision controller can communicate data using:

MODBUS (serial) commands.
VisiLogic's Communication Protocol FB, which enables Vision controllers to communicate data with most external serial devices, such as bar-code readers and frequency converters, via their proprietary protocols.
SMS messages. The SMS FB enables text messages, including variable data, to be sent and received via GSM modems.
e-mail via GPRS (Enhanced Vision only).
GPRS cellular network, to transmit IP packets of data.

Modem Tips

Notes ♦	The PC-modem cable is not the same type of cable used to connect between the controller and the modem. Ensure that the cable used to connect the PC to the modem provides connection points for all of the modem's pins.
♦	If calls are routed via a switchboard, note that the switchboard settings may interfere with communications. Consult with your switchboard provider.
♦	If, within the modem initialization strings, the parameter S7 is too short to permit the PLC's modem to answer, an error will result. For example, if this parameter is set as S7=30, the PC modem will wait for 3 seconds to receive an answer from the PLC's modem. If the PLC modem does not answer before the 3 seconds have elapsed, the S7=30 parameter is exceeded, and the PC modem returns the No Carrier error.
♦	PC/PLC modem communications: Both PC and controller must use the same type of modem: either landline or GSM. Internal PC modems must be used in conjunction with the driver provided by the modem's manufacturer.
♦	Standard Vision Division Controllers in this division can only support a single modem. You can connect a modem to any COM port. However, note that SB 184 TX Success and SB 185 TX Failed indicate message transmission status regardless of the actual COM port connected to the modem. Enhanced Vision Division Controllers in this division can support a modem on each COM port. Each port is linked to a Succeed and Fail SB: COM1: SB 184 and SB 185, COM2: SB186 and SB 187, COM3: SB 188 and SB 189.
	When working with Enhanced Vision controllers: Set the baud rate in both Modem Services and in COM Init to 57600. In addition, run the Prepare PLC Modem procedure with the baud rate set to 57600. Com Init: - Select Ignore Break - Time Out Reply: set to a minimum of 6 seconds.
♦	Known compatibility issue: Sony Ericsson Modems. Unitronics products are compatible with the following Sony Ericsson Modems: Model GT47 R5xxxx and higher Model GM29 R6xxxx and higher Unitronics cannot guarantee compatibility with other models, such as Sony Ericsson Modem model GM29 R4xxxx.