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HART Communication Commands

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The HART Command Set provides uniform and consistent communication for all field devices. The command set includes three classes: Universal, Common Practice, and Device Specific. Host applications may implement any of the necessary commands for a particular application.

Universal Commands
All devices using the HART Protocol must recognize and support the universal commands. Universal commands provide access to information useful in normal operations (e.g., read primary variable and units).

Common Practice Commands
Common Practice commands provide functions implemented by many, but not necessarily all, HART communication devices.

Device Specific Commands
Device Specific commands represent functions that are unique to each field device. These commands access setup and calibration information, as well as information about the construction of the device. Information on Device Specific commands is available from device manufacturers.

The table below gives a list of the common HART commands encountered:

Universal Commands
Common Practice Commands
Device Specific Commands
 Read manufacturer and device  type
 Read selection of up to  four  dynamic variables
 Read or write low-  flow  cut-off
 Read primary variable (PV) and  units
 Write damping time  constant.
 Start, stop or clear  totalizer
 Read current output and percent of  range
 Write device range values
 Read or write density  calibration factor
 Read up to four predefined dynamic  variables
 Calibrate (set zero, set  span)
 Choose PV(mass, flow  or  density)
 Read or write eight character tag,  16 character  descriptor, date.
 Set fixed output current
 Read or write materials or  construction information
 Read or write 32-character  message.
 Perform self-test
 Trim sensor calibration
 Read device range values, units and  damping  time constant.
 Perform master reset
 PID enable
 Read or write final assembly  number.
 Trim PV zero
 Write PID setpoint
 Write polling address
 Write PV unit
 Valve characterization

 Trim DAC zero and gain
 Valve set point

 Write transfer function  (square  root/linear)
 Travel limits

Write sensor serial  number
 User units

 Read or write dynamic  variable assignments
 Local display information

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