User's Manual

Appendix C: Communications via PROFIBUS
C.10 Diagnostics
SITRANS LR250 (PROFIBUS PA)
244 Operating Instructions, 01/2014, A5E32221386-AB
C.10.6
Acyclic data
SITRANS LR250 supports up to four simultaneous connections by a Class 2 Master (C2
connection). It supports one connection by a Class 1 Master (C1 connection).
In order for a Class 1 Master to read parameters from a device, it needs to know the slot and
absolute index of the parameter.
The parameters are all listed in SIMATIC PDM under Help. If you do not have SIMATIC PDM
you can download the EDD (Electronic Device Description) and reference the HTML help file
directly.
To find the slot and index numbers via SIMATIC PDM, go to Help > Communications, and select
the appropriate block from the list. For each parameter, the slot and the relative index is listed.
For example.
AIFB 1
Index
Parameter
Datatype
1
Static Revision No.
UNSIGNED_INTEGER (2)
Each block has a slot number and an Index Offset value.
Block Name
Slot
Index Offset
Physical block
0
16
Transducer block
0
77
AIFB 1
1
16
AIFB 2
2
16
To get the absolute index for any parameter, add the Index Offset for the appropriate block to
the relative index for that parameter. The parameter takes the slot number of the block in which
it is located.
For example:
● Parameter
Static Revision Number
has relative index = 1 and is located on AIFB1.
● It has Absolute Index = 17 (relative index 1 + index offset 16).
● It is located at Slot 1 (the slot number for AIFB 1).