41-621.1 HART
®
to Modbus
®
Adaptor Operating Manual 7
Supported Device Parameters
Not all of the parameters for a particular Magnetrol HART transmitter are supported by the HMA using
Modbus communication. For each device type, the parameters that are available have been chosen to
represent the most commonly for optimization and troubleshooting. The available parameters are
listed in Appendices L through S.
Full Device Configuration
Using a HART DD or DTM, the full range of HART transmitter parameters can be accessed to configure
an attached HART device. There are three ways to connect a HART host to the transmitter enclosed
with the HMA. In each case, the HART Poll Address of the attached device must be used for
communication rather than the Modbus poll address of the connected HMA.
1. A HART modem can be connected directly to the HART terminal block on the HMA. The HMA
will always act as a primary master on the HART loop. Therefore, if connecting another HART
host to the terminal HART block, that additional host must either be capable of automatically
setting itself to be a secondary master, or be manually configured as a secondary master. Note
that the HART terminal block has a built-in 250-ohm resistor to facilitate HART communication.
See the section on using a DTM with the HMA.
2. The HMA is capable of passing HART commands using the RS-485 connection to the attached
devices.
3. A TTL-232R-3V3-AJ USB to TTL cable or equivalent can be connected between the computer
running the DD host or DTM frame (such as PACTware) and the audio jack on the electronics
module of the transmitter located underneath the LCD display. The HART host can be set as
either a primary or secondary master. This feature is available on the Model 706 Guided Wave
Radar, Model JM4 Magnetostrictive, and Model R96 Radar devices.
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