Siemens SIMATIC S7-1500/ET 200MP System Manual page 216

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 9- 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 type of CPU and 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, an S7-1500 CPU 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 stops execution of the job until a resource becomes free 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.
Automation system
System Manual, 01/2023, A5E03461182-AK
REQ STATUS/RET_VAL
0 W#16#7000
1 W#16#7001
Error code (e.g. W#16#80C3
for lack of resources)
Not rele- W#16#7002
vant
Not rele- W#16#0000, if no errors
vant have occurred.
Error code if errors oc-
curred.
Basics of program execution
9.2 Asynchronous instructions
BUSY DONE
0 0
1 0
0 0
1 0
0 1
0 0
ERROR
0
0
1
0
0
1
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