Technical data

Table Of Contents
Organization Blocks
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
1-23
1.13 I/O Redundancy Error OB (OB70)
Note
The I/O redundancy error OB (OB70) can only be used with H CPUs.
Description
The operating system of the H CPU calls OB70 when there is a loss of redundancy
on PROFIBUS DP (for example, a bus failure for the active DP master or when an
error occurs in the interface module of the DP slave) or when the active DP master
of DP slaves with connected I/Os changes.
The CPU does not change to the STOP mode if a start event occurs and OB70 is
not programmed. If OB70 is loaded and if the H system is in the redundant mode,
OB70 is executed on both CPUs. The H system remains in the redundant mode.
Local Data of the I/O Redundancy OB
The following table contains the temporary (TEMP) variables of the I/O redundancy
error OB. The variable names selected are the default names of OB70.
Variable Type Description
OB70_EV_CLASS BYTE Event class and IDs:
B#16#72: outgoing event
B#16#73: incoming event
OB70_FLT_ID BYTE Error code (possible values:
B#16#A2, B#16#A3
OB70_PRIORITY BYTE Priority class; can be assigned via
STEP 7 (hardware configuration)
OB70_OB_NUMBR BYTE OB number (70)
OB70_RESERVED_1 WORD Reserved
OB70_INFO_1 WORD Dependent on error code
OB70_INFO_2 WORD Dependent on error code
OB70_INFO_3 WORD Dependent on error code
OB70_DATE_TIME DATE_AND_TIME DATE_AND_TIME at which the OB
was called
The following table shows which event resulted in OB70 being started.
OB70_EV_CLASS OB70_FLT_ID Start Event of OB70
B#16#73 B#16#A2 Failure of a DP master or a DP master system respectively
B#16#73/B#16#72 B#16#A3 Loss of redundancy / return of redundancy of a DP slave