MVI69E-MBS ♦ CompactLogix™ Platform
MVI69E-MBS Backplane Data Exchange
Modbus Serial Enhanced Communication Module
User Manual
ProSoft Technology, Inc.
Page 74 of 159
5.4.2 Master Mode
In Master mode, the MVI69E-MBS module issues read or write commands to slave
devices on the Modbus network. These commands are user-configured in PCB; refer to
Modbus Port x Commands (page 44). This list is transferred to the module when the
module receives its configuration from the processor.
The commands can also be issued directly from the CompactLogix or MicroLogix 1500-
LRP processor (Special Command Blocks).
Command status is returned to the processor for each individual command in the
command list. The location of this command status list i
n the module’s internal database
is user-defined. The following flow chart and associated table describe the flow of
command data into and out of the module.
Step
Description
1
Upon module boot-up, the Master driver obtains configuration data from the MBS
controller tags. The configuration data retrieved includes port configuration and the
Master Command List.
Special Commands can be issued directly from the CompactLogix or MicroLogix 1500-
LRP processor using Event Commands and Command Control. These command values
are used by the Master driver to determine the types and order of commands to send to
slaves on the network.
2
After configuration, the Master driver begins transmitting read and/or write commands to
slave nodes on the network. If the Master driver is writing data to a slave, the data for the
write command is retrieved from the module’s internal database.
3
Once the specified slave has successfully processed the command, it returns a response
message to the Master driver for processing.
4
Da
ta received from a slave in response to a read command is stored in the module’s
internal database.
5
Status is returned to the processor for each command in the Master Command List.