Remote Operation
Instrument Status Reporting IEEE 488.2 Basics 5
5-13
5-27. Event Register Conditions
The Status Byte summary bits direct the application program down the structure towards
causal events.
ESB and MAV are standard IEEE-488 features, described in detail in “Instrument Status
Reporting IEEE 488.2 basics”, OSS and QSS are features of the SCPI structure, described
in “Instrument Status Reporting SCPI Element”.
5-28. Access via the Application Program
Referring to figure at the beginning of this sub-section take as an example the main Event
Status register:
• Enabling the Events
The main Standard-Defined Event Status Register has a second Event Status Enable
Register. A program command (*ESE phs Nrf ) can be used to set the state of the bits in
the Enable register. This enables or disables the events, which will set the main
register's summary bit true.
• Reading the Enable Register
A query command (*ESE?) permits the application program to read the state of the
Enable register, and hence find out which events are enabled to be reported.
• Reading the Main Register
Another query command (*ESR?) reads the state of the main Standard-Defined register,
to discover which event has occurred (for example, has caused the summary bit to be set
true). Reading this register clears all its bits.
• Reporting the Event
If an event is to be reported via the SRQ, its corresponding enable bit will have been set
true, (using the number Nrf ). Each bit in the Standard-Defined register remains in false
condition unless its assigned event occurs, when its condition changes to true and
remains true until cleared by *ESR? or *CLS. This causes the register's summary bit in
the Status Byte also to be set true. If this bit is enabled, then the Status Byte bit 6 (MSS/
RQS) will be set true, and the instrument will set the IEEE-488 bus SRQ line true.
• SCPI Status Registers
The two SCPI Status registers operate in the same way, using the appropriate program
commands to set the enable registers, and query commands to discover the condition of
the registers (the 6100B does not make use of these registers).
• Subsequent Action
Thus the application programmer can enable any assigned event to cause an SRQ, or not.
The controller can be programmed to read the Status Byte, using a serial poll to read the
Status Byte register and the true summary bit (ESB or MAV). The application program
then investigates the appropriate event structure until the causal event is discovered. The
detail for each register is expanded in the following paragraphs, and in the command
descriptions.
5-29. Instrument Status Reporting IEEE 488.2 Basics
5-30. IEEE 488.2 Model
This develops the IEEE 488.1 model into an extended structure with more definite rules.
These rules invoke the use of standard Common messages and provide for device-dependent
messages. A feature of the structure is the use of Event registers, each with its own enabling
register as shown in “Retrieval of Device Status Information”.
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