User and Programming Manual - Rev H
California Instruments
P Series
May 2000
81
The PON bit in the Standard Event Event register is set whenever the AC source is turned on.
The most common use for PON is to generate an SRQ at power-on following an unexpected
loss of power.
16.3 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
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.
16.4 Examples
The following section contains examples of commonly used operations involving the status
registers.
You can determine the reason for an MSS bit set by the following actions:
Step 1 :
Determine which summary bits are active.Use
*STB?
Step 2 :
Read the corresponding Event register for each summary bit to determine which
events caused the summary bit to be set. Use:
ESR?
Note:
When an Event register is read, it is cleared. This also clears the corresponding
summary bit.
Step 3 :
Remove the specific condition that caused the event. If this is not possible, the event
may be disabled by programming the corresponding bit of the status group Enable.
