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Communications Setup
372 SPU 780 01EMAN May 2002 69
Setting the
Modbus Modem
Parameters
In the Communications Setup dialog:
Modbus 10-bit
Configurations
These Modbus configurations provide 10 bits per data package:
Step Action
1 Select the Modbus tab and set the communications parameters (see
Configuring Modbus Communications for parameter descriptions).
2 The controller must have the same Modbus settings as the computer. Set
Modbus parameters for your PLC with the Ports tab of the Controller
Configuration window.
3 Set the Port parameter to show the computer port connected to the modem;
otherwise, ProWORX 32 won’t be able to locate it.
4 The Modbus configuration must send exactly 10 bits per data package to your
modem. (See Modbus 10-bit Configurations below.)
Modems generally expect 10 bits in a data package; however, the Modbus
defaults (Even parity, RTU mode, and one stop bit) send 11 bits per package.
Change the Modbus settings to provide 10 bits per data package or ProWORX
32 will not be able to communicate with the modem. Alternatively, if your modem
supports large data packages, you can set its DIP switches to allow 11 bits per
data package (see your modem’s manual).
5 Select the type of modem from the Modem Type parameter drop-down. (See
Modem Type Descriptions below.)
6 To edit the modem parameters, click Modem Setup. The Modem Configuration
dialog appears. (For parameter descriptions, see below.)
Parameters ASCII Mode ASCII Mode RTU Mode
Start Bit 1 bit 1 bit 1 bit
Data 7 bits 7 bits 8 bits
Stop Bits: 1 1 bit 1 bit
Stop Bits: 2 2 bits
Parity: None 0 bits 0 bits
Parity: Odd or Even 1 bit
Total 10 bits 10 bits 10 bits