3.5.7 Number of connectable devices
The number of devices which can be connected to a bus strand can be calculated from the sum
of the maximum power consumption of the devices and the power available. By default,
assume 10 mA per device. For safety reasons, plan for a power reserve. Otherwise you run the
risk of a defective device overloading the bus with an increased power consumption. This can
interrupt the power supply and communication with the functioning nodes. The amount of
power reserved is based on the nominal power increase given by the manufacturer in case of
failure.
3.5.8 Assigning the device addresses
So that the connected process devices can be distinguished from one another, each device has
its own address.
Be sure that the device addresses are set before operating two or more field devices on the bus.
Each address may only be given once to make sure they are unique.
Principally, the address range is from 1 to 125. The address 126 is set for the delivery state.
Normally, masters in PROFIBUS systems receive lower addresses. Therefore, we recommend
starting at 30 when assigning addresses to the positioners. Either use the keys on the
positioner or the SIMATIC PDM software via the bus to set the addresses. In the last case, a
new positioner is always connected to the bus and the new address is set via the software. The
next positioner is then connected to the bus and processed the same way.
We recommend writing the set address on the field device with a wipe resistant pen.
See also
Process instrumentation catalog (http://www.siemens.com/processinstrumentation/catalogs)
Description
3.5 PROFIBUS PA
SIPART PS2 with PROFIBUS PA
Operating Instructions, 05/2019, A5E00127926-AC 37
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