Why do I receive information on the status of 27 configured blocks
at maximum, when parametrizing the partial list SZL 0E91 of system
Partial list 0E91 of the system function SFC51 does only apply for
With parametrization of partial list SZL 0E91 of the system
function SFC51 you receive status information of all
configured blocks - independently of whether or not they are
plugged to the rack.
For each configured block, 8 words or 16 bytes must be reserved -
independently of whether or not these are plugged in the rack.
Below table describes the structure of the data set of SZL
partial list 0E91.
In case of central
number of the block of the physical address
In case of distributed setup with
ID of DP master system, stations number
case of distributed setup with PROFINET IO:
the last two digits of the ID of the PROFINET IO system, stations
In case of central and
distributed setup with PROFIBUS DP:
number of the slot and of the submodule slot
In case of distributed setup with PROFINET IO:
number of interface
||First assigned logical I/O address (basic
||PROFINET IO: setpoint type,
||PROFINET IO: actual type, reserved
||Area ID / Width of block|
Tab. 1: Structure of a Data
Set of the Partial List with SZL ID:= W#16#xy91
The general limitation of SFC51 is ca. 440 Byte.
For a configuration of 27 blocks you therefore receive an overall
size of 27 * 16 bytes = 432 bytes. Hence details of block status of
at maximum 27 blocks is possible. Further blocks cannot be
Further information on the structure of the data set of the
partial list SZL you also find in the online help of STEP 7 in
"SZL-ID W#16#xy91 - Block status information".
SZL-ID, SFC51 "RDSYSST" (read system status)