Reference Manual
00809-0100-4690, Rev FC
June 2011
3-15
Rosemount 2088 and 2090
Burst Mode Burst Mode sets the transmitter to maintain digital contact with a Digital
Control System that has custom software to support burst mode. When the
Rosemount 2088 transmitter is configured for burst mode, it provides faster
digital communication from the transmitter to the control system by eliminating
the time required for the control system to request information from the
transmitter.
Burst mode is compatible with use of the analog signal. Because HART
®
protocol features simultaneous digital and analog data transmission, the
analog value can drive other equipment in the loop while the control system is
receiving the digital information. Burst mode applies only to the transmission
of dynamic data (pressure and temperature in engineering units, pressure in
percent of range, and/or analog output in mA), and does not affect the way
other transmitter data is accessed.
Field Communicator
Access to information other than dynamic transmitter data is obtained through
the normal poll/response method of HART communication. A Field
Communicator or the control system may request any of the information that
is normally available while the transmitter is in burst mode. Between each
message sent by the transmitter, a short pause allows the Field
Communicator or a control system to initiate a request. The transmitter will
receive the request, process the response message, and then continue
“bursting” the data approximately three times per second.
Alarm and Saturation
Levels for Burst Mode
Transmitters set to burst mode handle saturation and alarm conditions
differently.
Alarm Conditions:
• Analog output switches to alarm value
• Primary variable is burst with a status bit set
• Percent of range follows primary variable
• Temperature is burst with a status bit set
Saturation:
• Analog output switches to saturation value
• Primary variable is burst normally
• Temperature is burst normally
Alarm and Saturation
Values for Multidrop
Mode
Transmitters set to multidrop mode handle saturation and alarm conditions
differently.
Alarm Conditions:
• Primary variable is sent with a status bit set
• Percent of range follows primary variable
• Temperature is sent with a status bit set
Saturation:
• Primary variable is sent normally
• Temperature is sent normally
4-20 mA Fast Keys
1, 4, 3, 3, 3
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