Network Topology - ICP DAS USA HRT-710 User Manual

3.2 Network topology

HART bus can operate in one of these two network configurations—point
to point or multi-drop.
1. Point to Point Mode :
In point to point mode, the analog signal is used to communicate one
process variable and the digital signal gives access to secondary variables
and other data that can be used for operations, commissioning, maintenance
and diagnostic purposes. Only one HART slave device can exist in HART bus
and the polling address must be zero.
2. Multi-drop Mode :
In multi-drop mode, all process values are transmitted digitally. The
polling address of all field devices must be bigger than 0 and between 1 ~
15. The current through each device is fixed to a minimum value (typically
4 mA). The maximum HART device number in HART bus is up to 15.
[ Note ]
1. The built-in resistor in HRT-710 is 250 Ohm with 1/4W. Therefore, HRT-
710 supports to connect the maximum 7 HART devices simultaneously. If
the HART devices in multi-drop mode are more than 7, then users need to
disconnect the built-in resistor in HRT-710 (prevent to burn down) and use
the external 250 Ohm resistor with 1W.
HRT-710 User Manual (Version 1.24, June/2015)
Figure 16: ―Point to Point‖ topology
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