Rockwell Automation 1794-APBDPV1 FLEX I/O PROFIBUS Adapter User Manual User Manual
Page 136
Publication 1794-UM064B-EN-P - May 2014
Additional HART Protocol Information 123
Start Character
The start character of a HART message indicates the frame’s format, the source
of the message, and if it is using burst mode. The 1794-APBDPV1 module does
not support burst mode.
HART Address
The Smart Transmitter Interface addresses HART field devices using either a
short or long frame address format, as specified by the HART delimiter byte. A
short frame address is one byte long. A long frame address is five bytes long and
includes a unique 32-bit identifier encoded within each field device by the
manufacturer.
HART field device addressing is device dependent. Some devices do not support
long frame addressing while others only recognize short frame addressing for
HART Command 0. In this situation, use HART Command 0 to determine the
long frame address, and then use long frame addressing for al other HART
commands. Consult the documentation provided with your field device for
details about the addressing formats it supports.
HART Command
This one-byte field specifies the HART command that is to be sent by the Smart
Transmitter Interface to the field device. Many commands are device dependent.
Consult the documentation provided with your field device for details about the
commands supported. Set this field to a device-recognizable command before
sending the packet to the Smart Transmitter Interface.
Start Character Byte Definitions
Frame Type
Short Frame Addressing
(hex)
Long Frame Addressing
(hex)
Master To Slave
02
82
Slave To Master
06
86
Burst Mode From Slave
01
81
Representative of HART Universal Commands
Universal Command
(dec)
Description
Expected Response
0
Read unique indentifier
Unique 32-bit device identifier,
revision levels, number of preambles
required
1
Read primary variable
Primary variable in floating point (IEEE
754 format)
2
Read primary variable current
and percent of range
Primary variable in milliamperes and
percents