Technical data

Table Of Contents
SFCs for Diagnostics
System Software for S7-300/400 System and Standard Functions - Volume 1/2
13-4
A5E00709327-01
13.3 Reading a System Status List or Partial List with
SFC 51 "RDSYSST"
Description
With system function SFC 51 "RDSYSST" (read system status), you read a system
status list or a partial system status list.
You start the reading by assigning the value 1 to the input parameter REQ when
SFC 51 is called. If the system status could be read immediately, the SFC returns
the value 0 at the BUSY output parameter. If BUSY has the value 1, the read
function is not yet completed.
Note
If you call SFC 51 "RDSYSST" in the diagnostic interrupt OB with the SSL-ID
W#16#00B1 or W#16#00B2 or W#16#00B3 and access the module that initiated
the diagnostic interrupt, the system status is read immediately.
With SFC 51 "RDSYSST" only complete data records are transferred.
System Resources
If you start several asynchronous read functions (the jobs with SSL_ID
W#16#00B4 and W#16#4C91 and W#16#4092 and W#16#4292 and W#16#4692
and possibly W#16#00B1 and W#16#00B3) one after the other at brief intervals,
the operating system ensures that all the read jobs are executed and that they do
not interfere with each other. If the limits of the system resources are reached, this
is indicated in RET_VAL. You can remedy this temporary error situation by
repeating the job.
The maximum number of "simultaneously" active SFC 51 jobs depends on the
CPU. You will find this information in /70/ and /101/.
Parameter Declaration Data Type Memory Area Description
REQ INPUT BOOL I, Q, M, D, L,
constant
REQ=1: Starts processing
SSL_ID INPUT WORD I, Q, M, D, L,
constant
SSL-ID of the system status list or
partial list to be read.
INDEX INPUT WORD I, Q, M, D, L,
constant
Type or number of an object in a
partial list.
RET_VAL OUTPUT INT I, Q, M, D, L If an error occurs while executing the
SFC, the RET_VAL parameter
contains an error code.
BUSY OUTPUT BOOL I, Q, M, D, L TRUE: Reading not yet completed.
SSL_HEADER OUTPUT STRUCT D, L See below.
DR OUTPUT ANY I, Q, M, L, D Destination area of the SSL list read
or the SSL partial list read:
If you have only read out the header
information of an SSL list,
you must not evaluate DR but
only SSL_HEADER.
Otherwise, the product of
LENTHDR and N_DR indicates
how many bytes were entered in DR.