Wednesday, July 13, 2011

Autoconfigured Communication Ports The RS-485 Port





The port of RS-485 has to be used for interrelating units on the link of I/O expansion for a child or parent PLC. The parameters of auto-configured port are set and can’t be changed in both these operating modes. The port of exp link can’t be set for I/O expansion in a single PLC; it has to be either used for communications of ASCII or disabled. The parameters of auto-configured for this port in single mode are for communications of ASCII.

The Port of RS-232
The 110CPU612 and 110CPU512 Micro PLCs have two ports of RS-232 communication, while the 110CPU411 and 110CPU311 models only have one. The parameters of auto-configured allocated to these ports base on both the model and the working mode of the PLC. If a PLC is in child or parent operating mode, the auto-configures of panel software one of the ports of RS-232 to a mode that supports communications between the ASCII input/output and PLC an device or a device of Modbus master.

The panel programming is judged the master device of Modbus, and the PLC is decided the slave device of Modbus. The port of RS-232 employs its DSR line to notify the PLC whether a Modbus master device or an ASCII device is linked in Modbus/ASCII toggling mode. When an ASCII device is attached to comm 1, the line of DSR suits INACTIVE and the port communicates data of 8-bit ASCII When a Modbus master device is linked to comm 1, the DSR line suits ACTIVE, and the port communicates data of 8-bit RTU. If the PLC is a model of 110CPU311 or 110CPU411 in child or parent mode, Modbus/ASCII toggle mode is auto-configured on the port of comm 1. If the PLC is a model of 110CPU512 or 110CPU612 in child or parent mode, Modbus/ASCII toggle mode is auto-configured on the port of comm 2, and the port of comm 1 is auto-configured for committed Modbus communications.

The ports of RS-232 are always auto-configured for dedicated communications of Modbus in the single-mode PLCs. This is because the port of RS-485 is auto-configured for ASCII, and only one port on the PLC which can be support communications of ASCII. All ports of RS-232 are auto-configured for 9600 baud communications, which allows you to connect a programming panel to the PLC at any port of RS-232. Tools that do not communicate through the protocol of Modbus cannot be exploited at a dedicated port of Modbus.



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