Basics of program execution
7.3 Asynchronous instructions
Distributed I/O system
System Manual, 12/2016, A5E03576849-AG
157
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 CREATE_DB.
①
The input parameter REQ starts the job to execute the asynchronous instruction.
②
The output parameter DONE indicates that the job was completed without error.
③
The output parameter BUSY indicates whether the job is currently being processed. When
BUSY =1, a resource is assigned for the asynchronous instruction. If BUSY = 0, then the re-
source is free.
④
The output parameter ERROR indicates that an error has occurred.
⑤
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.
Figure 7-3
Block parameters of asynchronous instructions using the instructions WRREC and
CREATE_DB as examples.
Summary of Contents for Simantic ET200SP
Page 1: ......