Appendix C: Communications via PROFIBUS
C.3 Bus termination
SITRANS LR250 (PROFIBUS PA)
266
Operating Instructions, 08/2014, A5E32221386-AC
C.3
Bus termination
Note
PROFIBUS PA cable shield MUST be terminated at both ends of the cable for it to work
properly. Please refer to the PROFIBUS PA User and Installation Guidelines (order number
2.092), available from:
PROFIBUS PA (
C.4
Power demands
To determine how many devices can be connected to a bus line, calculate the combined
maximum current consumption of all the connected devices: 15 mA for SITRANS LR250. Allow
a current reserve for safety.
C.5
PROFIBUS address
A unique PROFIBUS address identifies each device on the network. To set the PROFIBUS
address see Device Address (5.1.).
Note
•
It is possible to change the device address via a Class 1 master (for example, a PLC) and
lock the device address to prevent further changes.
•
If this Address Lock is on, the PA address cannot be changed. This lock can be
disabled only by performing an Address Reset.
Resetting the PROFIBUS address to 126
●
Via SIMATIC PDM:
1.
Open the menu Device – Master Reset and click on Reset Address to 126.
2.
Click on OK: the address will be reset to 126, and if the address lock was on, it will be
disabled.
●
Via the handheld programmer:
1.
Navigate to Service (4.) > Master Reset (4.1.). (You can enter the numeric value instead of
navigating via the Arrow keys.)
2.
Press RIGHT Arrow to open Edit Mode then scroll down to DEV ADDRESS and press RIGHT
Arrow to select it. The address will be reset to 126, and if the address lock was on, it will be
disabled.
3.
Press LEFT Arrow to exit.