12.2 Standard Event Status Group
This group consists of an Event register and an Enable register that are programmed by
Common commands. The Standard Event register latches events relating to interface
communication status. It is a read-only register that is cleared when read. The Standard
Event Enable register functions similarly to the enable registers of the Operation and
Questionable status groups.
Command Action
*ESE programs specific bits in the Standard Event Enable register.
*ESR? reads and clears the Standard Event register.
The PON bit in the Standard Event register is set whenever the AC source is turned on.
12.3 Status Byte Register
This register summarizes the information from all other status groups as defined in the IEEE
488.2 Standard Digital Interface for Programmable Instrumentation. The bit configuration is
shown in Table 10-6.
Command Action
*STB? reads the data in the register but does not clear it (returns MSS in bit 6)
The MSS Bit
This is a real-time (unlatched) summary of all Status Byte register bits that are enabled by
the Service Request Enable register. MSS is set whenever the AC source has one or more
reasons for needing service. *STB? reads the MSS in bit position 6 of the response but does
not clear any of the bits in the Status Byte register.
The MAV bit and Output Queue
The Output Queue is a first-in, first-out (FIFO) data register that stores AC source-to-
controller messages until the controller reads them. Whenever the queue holds one or more
bytes, it sets the MAV bit (bit 4) of the Status byte register.
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