Siemens SIMATIC ET 200pro Operating Instructions Manual page 55

Basics of program execution
6.2 Asynchronous instructions
Summary
The table below provides you with an overview of the relationships described above. It
shows in particular the possible values of the output parameters if execution of the
instruction is not complete after a call.
Note
You must evaluate the relevant output parameters in your program after each call
Table 6- 3 Relationship between REQ, STATUS/RET_VAL, BUSY and DONE during a "running" job.
Seq. no. Type of call
of the call
- Idle
1 First call
2 to (n - 1) Intermediate call
n Last call
Use of resources
Asynchronous instructions use resources in the CPU during their execution. The resources
are limited depending on the instruction. The CPU can simultaneously process only a
maximum number of asynchronous instruction jobs. The resources are available again after
a job has been processed successfully or with errors.
Example: For the RDREC instruction, a CPU 1516pro-2 PN can process up to 20 jobs in
parallel.
If the maximum number of concurrent jobs for an instruction is exceeded, the following
occurs:
● The instruction returns the error code 80C3 (lack of resources) in the block parameter
STATUS.
● The CPU does not execute the job until a resource becomes available again.
Note
Lower-level asynchronous instructions
Some asynchronous instructions use one or more lower-level asynchronous instructions for
their processing. This dependence is shown in the tables below.
Please note that each lower-level instruction typically occupies one resource in the
instruction's resource pool.
54
REQ STATUS/RET_VAL
0 W#16#7000
1 W#16#7001
Error code (e.g. W#16#80C3 for lack of
resources)
Not relevant W#16#7002
Not relevant W#16#0000, if no errors have occurred.
Error code if errors occurred.
BUSY DONE
0 0
1 0
0 0
1 0
0 1
0 0
CPU 1516pro-2 PN (6ES7516-2PN00-0AB0)
Operating Instructions, 11/2019, A5E35873416-AC
ERROR
0
0
1
0
0
1