Wednesday, April 11, 2012

Data Flow between Module of MVI46-MCM and Processor of SLC





The flow data between the 2 pieces of hardware, module of MVI46-MCM and SLC processor and other nodes on the network of MODBUS under the different operating modes of module. Every port on the module is arranged to imitate a master device of MODBUS or a slave device of MODBUS. The operation of each port depends on this configuration.

Slave Driver
The Mode of Slave Driver lets the module of MVI46-MCM to react to data write and read commands issued by a master on the network of MODBUS.

Description of Step
1. The driver of MODBUS slave port obtains the information configuration from the processor of SLC. This information organizes the serial port and describes the characteristics of slave node.
2. A device of Host for instance the PLC of Rockwell Automation or an application of HMI issues a writes or read command to the node address of module. The port driver be eligible the message before receiving it into the module.
3. The data is directly transmitted to or from the internal database in the module after the module receives the command. The data is delivering of the database and a reaction message is built if the control is a read command. The data is written immediately into the database and the file of M1 and a reaction message is built if the control is a write command.
4. The response is issued to the initiate master node after the processing of data has been finished in Step 3.
5. Counters are available in the Status Block that permit the ladder logic program to determine the level of activity of the Slave Driver.

Mode of Master Driver
The module of MVI46-MCM distributes read or write commands to slave devices on the network of MODBUS in the mode of Master. These instructions are user-configured in the module through the Master Command List accepted from the processor of SLC or issued immediately from the processor of SLC.

The status of command is gone back to the processor for every individual control in the status block of command list. The status block location in the internal database of module is user-defined.

Description of Step
1. The driver of Master acquires data configuration from the processor of SLC. The data configuration got comprises the commands number and the List of Master Command. These assessments are utilized by the Master driver to decide the kind of commands to be shared to the other nodes on the network of Modbus.
2. The drivers of Master starts transmitting the commands of read and/or write to the other nodes on the network after configuration. The data for the command write is acquired from the internal database of module to construct the command if writing data to another node.
3. Presuming victorious processing by the node specific in the rule, a reaction message is accepted into the processing of Master driver.
4. Data accepted from the node on the network is transferred into the internal database of module and the file of M1, assuming a interpret command.
5. Status is gone back to the processor of SLC for every command in the List of Master Command.

The parameters needed to identify the virtual master port of Modbus. Refer to Specification of Modbus Protocol for a whole discussion of the content and structure of each instruction. Care has to be taken in creating each command in the predictable operation list of the module. The effects might not be as preferred if two commands write to the similar internal module database address.



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