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Remote Operation
7.4.7 *OPC?
Syntax
*OPC?
Description
This query returns an ASCII character “1” when all pending operations have
been finished.
Result
ASCII character “1”.
Possible error codes
None
Example 1
*OPC?
Result
“1”
Example 2
:SWIT1 4; SWIT2 4; *OPC?
Result
“0”
Timing
In example 2 the matrix did not have the time to execute the command. Hence
a “0” is returned. A subsequent *OPC? will return a “1” as shown in example 1.
The timing to execute a command depends on the length of the command (in
case of concatenated commands). In case of switching commands like on
example 2, the controller will first command each switch to set its new position,
then query each switch to ensure that the positions are closed and finally
respond with a “1” to the *OPC? query.
As a rule of thumb electromechanical switches require approximately 10-15ms
to switch position. But the *OPC? query will return a “1” only after the switches
have not only changed its positions, but rather also confirmed its position. So it
is safe to consider some safety margin and expect a response of “1” after about
70ms per switch. As an example if 2 switches are commanded, wait about
140ms before issuing an *OPC? query that will return a “1”.
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