User manual

MVI56-HART ♦ ControlLogix Platform Configuring the MVI56-HART Module
HART Multi-drop Master Communication Module User Manual
ProSoft Technology, Inc. Page 45 of 171
October 13, 2011
2.3 Hart Command Examples
This section describes two examples that shows how to configure HART commands. The
first example shows a read command (function code 3 - READ DYNAMIC VARIABLES)
and the second example shows a write command (function 34 - WRITE DAMPING
VALUE).
2.3.1 Example of HART Command Function 3
The following example shows how to configure a command function 3 (READ DYNAMIC
VARIABLES) to read the process variables from the HART slave device. According to the
HART specification, this command will return four floating-point variables:
Word High Byte Low Byte
0 Current (mA)
1
2 Primary Variable
3
4 Second Variable
5
6 Third Variable
7
8 Fourth Variable
9
The command also returns the following integer data:
Word High Byte Low Byte
0 Status Word
1 Primary Variable Units Code Second Variable Units Code
2 Third Variable Units Code Fourth Variable Units Code
So, this command will return the following number of words:
Parameter Data Type Direction Number of
Words
Database
Address
(this example)
Variable Results Floating Point Read from slave to MVI 10 240 (word address)
Status/Unit Codes Integer Read from slave to MVI 3 290 (word address)
The user can configure the command parameters as described in the following table in
order to correctly read the command 3 results to the module database:
Index Parameter Value Observation
1 Enable 1 The command is sent continuously
2 Float DB
Address
240 The floating point results will be copied to the internal
database starting at word-address 240 (from 240 to
249)
3 Poll Interval 0 The command is sent without any delay
4 Word Count 10 The command returns 10 words of floating point data
5 Swap Code 3 The bytes in each returned floating point word are
swapped