Conventional Two-Wire RS-485 Network: The conventional two-wire RS-485 network uses a DIP SWITCH selectable converter to convert host RS-232 or USB signal to a two-wire RS-485 signal. The baud rate
and data format must be set to a fixed value for the whole network. For
example, the user can choose baud rate=9600 and data format=10 bit per character. This limitation is inconvenient for some real world applications. The 7000 series, Adam 4000 series, Nudam 6000 series and DATAFORTH 9B series all use a 10-bit format. Some conventional PLC use 11-bit data format and some weight scale equipment uses 12- bit. If the host-PC has to send command to remote modules, PLC and weight scale equipment, one possibility is to use three independent two-wireRS-485 networks. However, this may increase the system cost and reduced the system reliability.
An other option for the user is to use many modules in the same two- wire RS-485 network for real world applications. All these modules must communicate at the same baud rate in a conventional system. Some of those modules may be very close to the host-PC and will be able to communicate at a high baud rate. Some modules may be far away from the host-PC and will communicate at a low baud rate. Because only one speed is valid in the RS-485 network, the high-speed modules should be forced to communicate at a low speed baud rate. In other words, the performance of the whole system should be decreased.
The 7000 Series RS-485 Network: The 7000 RS-485 network is the most powerful and flexible two-wire RS-485 network in the world. It is a multiple baud rate and multiple data format network system. That is to say, all the remote modules mentioned above, PLCs and weight scale equipment share the same RS-485 network. The 7520, RS-232 to RS- 485 converter, equips a “Self Tuner” inside, therefore it can detect the baud rate and data format automatically and control the direction of the RS-485 network precisely. Therefore the user can connect all this equipment to the same RS-485 network. This method will greatly reduce system cost and increase reliability.
7000 Bus Converter User Manual (version 1.2,Feb/2003, 7PH-006-10) --------------- | 10 |
