Endress+Hauser HMX50 - Page 16

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Endress+Hauser
HART Loop Converter HMX50
Polling Mode (command and answer)
The isolated barrier deactivates the burst configuration of the field device. The isolated
barrier performs the field device query using HART command 3. See chapter 3.4.6.
Procedure to Restore Burst Mode
If the isolated barrier does not receive any more data from the field device in burst mode,
the following actions are taken:
• The isolated barrier switches to polling mode.
• The isolated barrier checks whether another HART master has started in the query signal
circuit. If the isolated barrier has detected a HART master, the restoring of burst mode is
interrupted.
• If the isolated barrier does not detect any other HART masters, the isolated barrier
attempts to activate burst mode.
• As soon as the isolated barrier receives a burst message from the field device, the isolated
barrier switches from polling mode to burst mode.
This process enables other HART masters to deactivate burst mode momentarily for service
work.
Time Out (communication loss)
When the timeout time has been exceeded in the absence of communication, all outputs
switch to the defined safe state. Timeout can be adjusted.
BA00371FEN_1417.fm Page 16 Tuesday, August 15, 2017 4:08 PM