Siemens SIMATIC S7-1500 System Manual page 232

Basics of program execution
9.5 Asynchronous instructions
Status of an asynchronous instruction
An asynchronous instruction shows its status via the block parameters STATUS/RET_VAL and
BUSY.​ Many asynchronous instructions also use the block parameters DONE and ERROR.
The figure below shows the two asynchronous instructions WRREC and RD_DPARA.
①
②
③
④
⑤
Figure 9-7 Block parameters of asynchronous instructions using the instructions WRREC and RD_DPARA
as examples.
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
The output parameters of an synchronous instruction can change on every call.
You therefore evaluate the relevant output parameters after each call of the asynchronous
instruction.
Table 9-6 Relationship between REQ, STATUS/RET_VAL, BUSY and DONE during a "running" job.
Seq. no. of Type of call
the
call
1 First call
232
The input parameter REQ starts the job to execute the asynchronous instruction.
The output parameter DONE indicates that the job was completed without error.
The output parameter BUSY indicates whether the job is currently being executed. When
BUSY=1, a resource is allocated for the asynchronous instruction. When BUSY= 0, the resource
is free.
The output parameter ERROR indicates that an error has occurred.
The output parameter STATUS/RET_VAL provides information on the status of the job execu­
tion. The output parameter STATUS/RET_VAL receives the error information after the occur­
rence of an error.
REQ STATUS/RET_VAL
1 W#16#7001
Error code (e.g. W#16#80C3
for lack of resources)
BUSY DONE
1 0
0 0
System Manual, 11/2022, A5E41814787-AD
ERROR
0
1
S7-1500R/H redundant system