Network and Remote Operation
R&S
®
FSW
625
User Manual 1173.9411.02 ─ 19
As a general rule, send commands and queries in different program messages.
Example: Overlapping command with *OPC
The instrument implements
INITiate[:IMMediate]
as an overlapped command.
Assuming that
INITiate[:IMMediate]
takes longer to execute than
*OPC
, sending
the following command sequence results in initiating a sweep and, after some time,
setting the
OPC
bit in the
ESR
:
INIT; *OPC.
Sending the following commands still initiates a sweep:
INIT; *OPC; *CLS
However, since the operation is still pending when the instrument executes
*CLS
, forc-
ing it into the "Operation Complete Command Idle" State (OCIS),
*OPC
is effectively
skipped. The
OPC
bit is not set until the instrument executes another
*OPC
command.
10.1.6.1
Preventing Overlapping Execution
To prevent an overlapping execution of commands, one of the commands *OPC,
*OPC? or *WAI can be used. All three commands cause a certain action only to be
carried out after the hardware has been set. By suitable programming, the controller
can be forced to wait for the corresponding action to occur.
Table 10-3: Synchronization using *OPC, *OPC? and *WAI
Com-
mand
Action
Programming the controller
*OPC
Sets the Operation Complete bit in the ESR
after all previous commands have been exe-
cuted.
●
Setting bit 0 in the ESE
●
Setting bit 5 in the SRE
●
Waiting for service request (SRQ)
*OPC?
Stops command processing until 1 is
returned. This is only the case after the Oper-
ation Complete bit has been set in the ESR.
This bit indicates that the previous setting has
been completed.
Sending *OPC? directly after the command
whose processing should be terminated
before other commands can be executed.
*WAI
Stops further command processing until all
commands sent before *WAI have been exe-
cuted.
Sending *WAI directly after the command
whose processing should be terminated
before other commands are executed.
Command synchronization using *WAI or *OPC? appended to an overlapped com-
mand is a good choice if the overlapped command takes only little time to process. The
two synchronization techniques simply block overlapped execution of the command.
For time consuming overlapped commands it is usually desirable to allow the controller
or the instrument to do other useful work while waiting for command execution. Use
one of the following methods:
*OPC with a service request
1. Set the OPC mask bit (bit no. 0) in the ESE: *ESE 1
Remote Control Basics
