User Manual

Siemens Building Technologies PROFIBUS DP/P-bus link
Building Automation User's guide 3-7
3.3 Diagnostics using the EMX block
Field of application
This module can be used to check module-specific faults in a DP/P-bus link.
Description of functions
• When a fault in the P-bus I/O modules occurs or is cleared, the DP/P-bus link triggers
diagnostics function OB 82. OB 82 then calls system function SFC 13 to call up the di-
agnostics for the DP subscriber whose basic module address is “B-ADR”.
• When the CPU starts up, it also calls system function SFC 13 for a diagnosis of the
DP/P-bus link.
• The data received from the diagnostic SFC also includes the appended common faults
of the individual I/O modules; these are stored in a specific data area.
• The module faults are read one byte at a time from this data area in the cyclical part of
the program, and transmitted to outputs S 1-8. A common fault message for all the I/O
modules engineered in the DP/P-bus link is transmitted to output ST-SAM.
• It is advisable to connect an integer resolution block for access to the faults from individ-
ual channels.
Bit “0” of the outputs contains the fault from the module with the lowest number.
Bit “7” contains the fault from the module with the highest number
(e.g. for output S 1-8, Bit 0 = Module 1 and Bit 7 = Module 8).
Important The block may be called once only for each DP/P-bus link.
Mounting location:
Anywhere below the CPU “Typical” block structure.