User manual

Reference MVI56-HART ♦ ControlLogix Platform
User Manual HART Multi-drop Master Communication Module
Page 90 of 171 ProSoft Technology, Inc.
October 13, 2011
5.2.6 Master Driver
The master driver supported on each application port of the module emulates a HART
master device. Configuration of each port is independent and should be connected to
different HART networks. Up to 15 devices can be connected to each channel. Control of
the slave devices by the master port is using a user-constructed command list auto-
polling, if enabled. Data for these commands is sourced from the module’s database.
Data read from the slave devices is placed in the module’s database. The following
diagram shows the operation of the master driver:
1 The master driver is configured as specified by the HART.CFG file
2 The master will construct control commands using the data in the database
3 The master will send these commands and read requests out on the network
4 Response messages generated by controlled devices on the network are received by
the master driver
5 Read data received by the master is passed to the module’s database and passed to
the processor
6 Additionally, status data for the module is passed to the processor
HART Command List
The HART Command List specifies the commands to be executed to the HART devices
connected to a channel. A HART command can be seen as an outgoing message to the
HART devices that provides Write Data for a specific command or a response message
that carries process data (Read Data) back to the module. The MVI56 module supports
three kinds of data blocks in the Universal and Common Practice commands. These data
blocks are:
 Integers
 IEEE 754 Floating Point Numbers (32 bits)
 Packed ASCII character strings
The Packed ASCII character strings are unpacked and placed with the integers data
block.
For all commands, it is possible to select where the Write Data comes from; it can be in
the module’s internal database or it can be configured as a fixed data block in the
command.