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NRT
Instrument Model and Command Processing
1080.9506.02
3.49
E-6
3.6.5 Output
Unit
The output unit collects the information requested by the controller, which it receives from the data set
management. It processes it according to the SCPI rules and makes it available in the output buffer. If
the information requested is longer, it is made available "in portions" without this being recognized by
the controller.
If the instrument is addressed as a talker without the output buffer containing data or awaiting data from
the data set management, the output unit sends error message "Query UNTERMINATED" to the status
reporting system. No data are sent on the IEC bus, the controller waits until it has reached its time limit.
This behavior is specified by SCPI.
3.6.6
Command Sequence and Command Synchronization
What was said above makes clear that overlapping execution is possible in principle for all commands.
Equally, setting commands within one command line are not absolutely serviced in the order in which
they have been received.
In order to make sure that commands are actually carried out in a certain order, each command must
be sent in a separate command line, that is to say, with a separate IBWRT()-call.
In order to prevent an overlapping execution of commands, one of commands *OPC, *OPC? or *WAI
must be used. All three commands cause a certain action only to be carried out after the hardware has
been set and has settled. By a suitable programming, the controller can be forced to wait for the re-
spective action to occur (cf. Table 3-15).
Table 3-15
Synchronization with *OPC, *OPC? and *WAI
Com-
mand
Action after the hardware has settled
Programming the controller
*OPC
Setting the operation-complete bit in the ESR
- Setting bit 0 in the ESE
- Setting bit 5 in the SRE
- Waiting for service request (SRQ)
*OPC?
Writing a "1" into the output buffer
Addressing the instrument as a talker
*WAI
Executing the next command
Note: The IEC/IEEE-bus handshake is not
stopped
Sending the next command
An example for command synchronization can be found in Annex D, "Programming Examples".
深圳德标仪器
135-1095-0799
Содержание NRT 1080.9506.02/.62
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