Technical data

Generating Block-Related Messages
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
24-37
Operating principle
If you have not selected a sufficiently large SYS_INST target area when you called
the SFC 105 in MODE=1 or MODE=3, it contains the content of all currently
occupied system resources selected via MODE parameter.
High system load on resources will cause a correspondingly high SFC runtime.
That is, a high load on CPU performance may result in overshoot of the maximum
configurable cycle monitoring time.
You can work around this runtime problem as follows: Select a relatively small
SYS_INST target area. RET_VAL=W#16#0001 informs you if the SFC cannot
enter all system resources to be read in SYS_INST. In this case, call SFC 105 with
MODE=0 and the same SI_ID as for the previous call until the value of RET_VAL is
W#16#0000.
Note
Since the operating system does not coordinate the SFC 105 calls that belong to
the read job, you should execute all SFC 105 calls with the same priority class.
Structure of the Target Area SYS_INST
The target area for the fetched occupied system resource must lie within a DB. You
should appropriately define the target area as a field of structures, whereby a
structure is constructed as follows:
Structure
element
Data type Description
SFC_NO WORD no. of the SFC that occupies the system resource
LEN BYTE Length of the structures in bytes, incl. SFC_NO and LEN: B#16#0C
SIG_STAT BOOL Signal state
ACK_STAT BOOL Acknowledgement status of the incoming event (positive edge)
EV_ID DWORD Message number
CMP_ID DWORD Partial system ID