Tuesday, April 10, 2012

General Concepts MVI46-MCM SLC Platform Modbus Communication Module





The following articles explains some concepts that are vital for understanding the MVI46-MCM module operation.
1. On the module power up starts carrying out the below of logical functions:
2. Initialize the components of hardware
• Initialize backplane driver of SLC
• Check and test all RAM
• Initialize the serial ports of communication
3. Hang around for configuration module from the processor of SLC
4. Assign and initialize space of Module Register
5. Allow Slave Driver on ports selected
6. Allow Master Driver on chosen port if configured
After the module has established the Configuration of Module, the module will initiate communicating with other nodes on the network, dependent on the configuration.

About the Protocol of MODBUS
MODBUS is a commonly-used protocol firstly developed by Modicon in 1978. Ever since that time, the protocol has been implemented as a standard through the industrial automation. The original specification of MODBUS utilizes a serial connection to correspond commands and data between Slave and Master Devices on a network. Later developments to the protocol let statement over other networks types.

MODBUS is a protocol of Master or Slave. The Master begins a link to the remote Slave. The Master transfers the commands of MODBUS to the Slave when the connection is created. The module of MVI46-MCM can operate as a Slave and as a Master.

The module of MVI46-MCM also operates as a module of input/output between itself and the backplane and processor of Rockwell Automation. The module utilizes an internal database to transfer data and commands between the Master and Slave devices and processor on networks of MODBUS.

Main Logic Loop
In the lead completing the process of power up configuration, the module goes into a countless loop that executes the following functions:


SLC Processor Not in Run
When the module senses that the processor has run out of the Run mode (that is, error or PGM), the ports of Modbus will be shut down. The module will restart communications on the network when the processor is come back to a state of running. No backplane data transfers happen when the processor is not in mode of run.

Data Transfer of Backplane
The module of MVI46-MCM corresponds directly over the backplane of SLC. All data for the module is enclosed in the M1 file of module. Data is shifted between the processor of SLC and the module across the backplane using the M1 files of module. The scan rate of SLC and the load of communication on the module decide the update frequency of the M-files. The instruction of COP can be utilized to move data between the M1 file of module and user data files.

The below illustration demonstrates the method of data transfer utilized to move data between the processor of SLC, the module of MVI46-MCM and the network of MCM. All data moved between the processor over and the module the backplane is throughout the files of M0 and M1. Ladder logic have to be written in the processor of SLC to interface the M-file data with data described in the data files of user-defined in the SLC. All data utilized by the module is saved in its internal database.

User data included in this database is constantly interpret from the file of M1. The data configuration is only keep posted in the file of M1 after every configuration demand by the module to the SLC. All of the data in the file of M1 is presented to devices on the networks of Modbus Master or Slave. This authorizes data to be moved from these devices to the SLC with the data area of user. In addition, the devices of remote can adjust the configuration of module, interpret the data status, and issue control commands. Identification of block codes defines particular functions to the module.

All data moved between the processor and the module over the backplane is from beginning to end the files of M0 and M1. Ladder logic have to be written in the processor of SLC to interface the data of M-file with data described in the user-defined files of data in the SLC. All data utilized by the module is saved in its internal database.

Normal Data Transfer
This module version provides for direct admission to the data in the module. All of the data associated to the module is saved in the M1 file of module. Use the instruction of COP to duplicate data from the M1 file of module to a user data file to read data from the module. Utilize the instruction of COP to duplicate data from a user file to the M1 file of module to write data to the module. Registers 0 - 4999 should be utilized for user data. All of the other registers are kept for other functions of module.


Labels:

Newer Post Older Post Home

You may also like these ebook:

Get Free PLC eBook directly sent to your email,
and email subscription to program-plc.blogspot.com




We hate SPAM. Your information is never sold or shared with anyone.

Your Email Will Be 100% Secured !