R&S
®
CMW 500 Remote Control
Status Reporting System
Operating Manual 1202.3986.32 – 03 109
Initiating an SRQ
As shown in the graphical overview, an SRQ is initiated if one or several of bits 2, 3, 4,
5 or 7 of the status byte are set and enabled in the SRE. Each of these bits
summarizes the information of a further register, the error queue or the output buffer.
The ENABle parts of the status registers can be set such that arbitrary bits in an
arbitrary status register initiate an SRQ. To use the possibilities of the service request
effectively, all bits in the enable registers SRE and ESE should be set to "1".
Example: Use *OPC to generate an SRQ
1. Set bit 0 in the ESE (Operation Complete).
2. Set bit 5 in the SRE (ESB).
3. Insert *OPC in the command sequence.
As soon as all commands preceding *OPC have been completed, the instrument
generates an SRQ.
The SRQ is the only possibility for the instrument to become active on its own. Each
controller program should set the instrument such that a service request is initiated in
the case of malfunction. The program should react appropriately to the service
request.
5.6.4.2 Serial Poll
In a serial poll, the controller queries the STatus Bytes of the devices in the bus system
one after another. The query is made via interface messages, so it is faster than a poll
by means of *STB?.
Serial poll procedure
The serial poll method is defined in IEEE 488.1 and used to be the only standard
possibility for different instruments to poll the status byte. The method also works for
instruments which do not adhere to SCPI or IEEE 488.2.
The Visual BASIC command for executing a serial poll is "IBRSP()".
The serial poll is mainly used to obtain a fast overview of the state of several
instruments connected to the controller.
5.6.4.3 Parallel Poll
In a parallel poll, up to eight instruments are simultaneously requested by the controller
by means of a single command to transmit 1 bit of information each on the data lines,
i.e., to set the data line allocated to each instrument to a logical "0" or "1".
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