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4.11
Status Reporting
The instrument is capable of reporting status events and errors to the controller, using the IEEE 488.1
Service Request function and the IEEE 488.2 Status Reporting structure.
The Status Byte
Status summary information is communicated from the device to the controller using the Status Byte
(STB). The STB is composed of single-bit summary-messages, each summary message summarizing an
overlying Status Data Structure. By examining the content of the STB, the controller gains some
information concerning the instrument's status.
The STB bits are defined as follows:
Bit 0: Unused
Bit 1: Unused
Bit 2: Error/event queue summary message (EVQ). This bit is set if the queue is not empty.
Bit 3: Questionable Status summary message.
Bit 4: Message Available (MAV) summary message. This bit is set whenever all or part of a
message is available for the controller to read. The controller may be ready to read the
response message before it is available, in which case it can either wait until this bit is
set, or it can start to read. In the second case, the controller timeout must be set so that
the read action will not be aborted before the message has been read.
Bit 5: Event Status Bit (ESB) summary message. This bit is set to indicate that one or more of
the enabled standard events have occurred.
Bit 6: Request Service (RQS). This bit is set when the device is actively requesting service.
Bit 7: Operation Status summary message. No Operation Status events are defined in the
instrument, and so this bit is never set.
The STB is read by the controller during a serial poll. If the RQS bit was set, it is then cleared. The STB
may also be read by the *STB? common query.
Service Request Enabling
Service request enabling allows the user to select which Status Byte summary messages may cause the
device to actively request service. This is achieved using the Service Request Enable Register, which is
an 8-bit register whose bits correspond to those of the STB. The RQS bit in the STB is set when a bit in
the STB is set, and its corresponding bit in the service request enable register is set.
The service request enable register is set using the *SRE common command, and read using the *SRE?
common query.
Standard Event Status Register
The Standard Event Status Register (SESR) is defined by IEEE 488.2. It is implemented in the instrument
as a byte, whose bits have the following definitions:
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