Modbus Communication Card
MODBUS communication card is connected to a single terminated MODBUS serial module. Termination module provides 4 serial communication with MODBUS. Each serial port 4 DIP switch for the specified protocol. The MODBUS communication card including message translating and formatting, message checking, responding to MODBUS controllers with proper acknowledgments, error, or success codes, and protocol data byte ordering. This built-in intelligence unburdens the PTR controller’s processor from the responsibility of managing the MODBUS network.
The card carry out bus check function of the input, output, and command operations. Data is sent two times, one normal and once abnormal. And then compare the results and the data will not take action unless the comparison is passed. If the check is not passed, the error status register is set up.
Contention check circuit to monitor the bus command signal occurred at the same time two or more than two of the command signal, if the synchronization occurs, an error bit is set in status word. Each MODBUS port can be configured to run as a MODBUS request to read and write data to the master device to transfer the MODBUS slave device, or as a MODBUS slave device from the MODBUS master to respond to the request.