Technical data

Table Of Contents
Generating Block-Related Messages
System Software for S7-300/400 System and Standard Functions - Volume 2/2
24-36
A5E00739858-01
24.16 Reading Dynamic System Resources with SFC 105
"READ_SI"
How dynamically occupied system resources develop when generating
messages with the SFCs 107 and 108
When messages are generated with SFCs 107 "ALARM_DQ" and 108
"ALARM_D", the operating system occupies temporarily system memory space.
For example, if you do not delete a FB that exists in the CPU with SFC 107 or
SFC 108 calls it may happen that corresponding system resources stay
permanently occupied. If you reload the FB with SFC 108 or SFC 108 calls, it may
happen that the SFCs 107 and 108 are not processed properly anymore.
Description
With SFC 105 "READ_SI" you can read currently used system resources occupied
with the SFCs 107 and 108 when messages were generated. This is done via the
values of EV_ID and CMP_ID used in this place. The values are passed on to
SFC 105 "READ_SI" in parameter SI_ID.
SFC 105 "READ_SI" has four possible operating modes that we explain in the
table below. Set the desired operating mode via the MODE parameter.
MODE Which of the system resources occupied by SFC 107/SFC 108 are read?
1 All (call of SFC 105 with SI_ID:=0)
2 The system resource occupied by the call of SFC 107-/SFC 108 with EV_ID:=ev_id (call of the
SFC 105 with SI_ID:=ev_id)
3 The system resource occupied by the call of SFC 107-/SFC 108 with CMP_ID:=cmp_id (call of
the SFC 105 with SI_ID:=ev_id)
0 Additional system resources that could not be read with the previous call in MODE=1 or
MODE=3 because you have specified a target field SYS_INST that is too small