Sunday, June 19, 2011

The Potential Problems Use of Modem with Mitsubishi FX PLC





Parameters of Communication Port
The modems were set to 7 data bits, even parity, 9600 baud, 1 stop bit and no flow control.

Potential Problems
1. The newest US Robotics of Black/Grey box Fax modem of Sportster voice 33.6 with personal voice mail has a recognized bug which will reason the modem that responds the call to pick up the call and fall it immediately. This is why the older cream US Robotics of Black/Grey box Fax modem of Sportster 28,800 Fax modem was utilized for the PLC end.
2. The newest US Robotics of Black/Grey box Fax modem of Sportster voice 33.6 with the personal voice mail showed a problem when using a lead phone from a diverse modem so always apply the lead complete.
3. The modem of PLC end may demonstrate a problem with settings of communication after it has been constructed and powered down. This is for the reason that the PLC needs settings of even parity, 1 stop bit, no flow control, 9600 baud, 7 data bits, nevertheless most default of systems to 1 stop bit, no flow control, 9600 baud, no parity, 8 data bits. It indicates that if the AT instructions are set using the incorrect communication settings or if the modem is reset, the modem will not recognize what settings to apply for the PLC connection serial port and will therefore use the defaults which are incorrect for an FX PLC. The way cause of this trouble is that the up to date modems change port of communications settings automatically to ensemble the tool talking to it. In the PLC system will not usually converse to the modem, it will only react when the modem is called, and consequently it does not recognize the settings. This trouble is not normally a problem but if it does obvious itself then the result is to use an extra AT command.



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