Siemens Simatic S7-1500R System Manual page 165

Basics of program execution
7.5 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 7-7
164
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 re-
source 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.
Block parameters of asynchronous instructions using the instructions WRREC and
RD_DPARA as examples.
S7-1500R/H redundant system
System Manual, 10/2018, A5E41814787-AA