ProSoft Technology MVI46-MBP - Manual (Page 48)

MVI46-MBP ♦ SLC Platform Reference
Modbus Plus Communication Module
Page 48 of 101 ProSoft Technology, Inc.
February 19, 2008
5.2.3 Data Flow between MVI46-MBP Module and SLC Processor
The following topics describe the flow of data between the two pieces of
hardware (SLC processor and MVI46-MBP module) and other nodes on the
Modbus Plus network under the module's different operating modes. Note that all
four modes can operate effectively simultaneously if desired. Under most likely
operating cases, the Global Input and Global Output tasks operate in conjunction
with either the Master or the Slave driver.
Global Data In Mode
When the Global Data In mode is operational, the MVI46-MBP module is
receiving Global Input data from up to 64 other nodes on the Modbus Plus
network. Each node is capable of transferring up to 32 words, and therefore, the
MVI46-MBP module is capable of accepting up to 2048 words in this manner.
The amount of data, and which slaves to collect it from, are all user-defined
through the Device Definition File. The following flow chart and associated table
show the flow of data into and out of the module.
0 40001
Modbus
Addresses
Database
Addresses
User Data
Files
Global Data
Driver
Register
Data
Processor Memory MBP Memory Backplane Interface
4000
4369
4370
7089
44001
44370
44371
47089
Status
Configuration Configuration
Data
Status
from module
Configuration
Status
3
1
2
6
Input
File
Map
Input
File
Map
Input File
Data
4
5
3999 44000
7161
7130 47130
47162
Input File Input File
Step Description
1 The Global In driver reads configuration data from the processor. This data includes the
Device Definition File that includes the node address data, the number of Global In words
and where to put this data in the module's internal database.
2 During the configuration process, the Input File Map is updated out of the configuration
file. The Input File Map informs the module which data registers in the internal database to
feed into the module's input image. This operational mode is independent of the Global In
mode but is commonly used to transfer global input data from other nodes directly to the
processor.
3 The Global In Driver monitors Global In data from other nodes on the network. If the data
matches one of the node addresses in the Device Definition File and is qualified in terms
of length, etc. the data is accepted.
4 After the data is accepted, the data is transferred into the module's internal database. The
user via configuration in the Device Definition File determines the location of the data.
5 As data is read from the other nodes on the network into the module, an asynchronous
process moves the data from the database into the module's input image. The values to
be moved are user determined via configuration of the Input File Map. Up to 32 words of
data can be transferred in this fashion.