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1.1.2.1 Point-to-point connection
When a master (communicator or HART modem with PC or MultiCONT) and a slave are alone in a system, we talk of a point-to-point connection
Transmitter
I+
I–
SH
L+
L–
MultiCONT
250
+U
s
Universal interface
RS485
In this case the flowing current is the output current of the transmitters, so if permitted by the loop voltage, even a local indicator can be included into the loop.
Essentially, the minimal voltage specified in the manual must be kept on the terminals of the transmitters.
Since the speed of transfer is 1200bit/sec, communication is slow, because the master queries and the slave responds. This can be speeded up if the querying is left
out, and the slave responds continuously every given period of time until the master stops the transfer in the break between 2 data transmissions. This is called “burst
mode”.
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