HP 53150A Series Programming Manual page 166

Chapter 5 Errors
Error Queue
Error Queue
As errors are detected, they are placed in an error queue. The error queue
is a first in, first out queue. That is, if more than one error has occurred,
the first error in the queue is read out with :SYST:ERR?. Subsequent
responses to :SYST:ERR? continue until the queue is empty.
If the error queue overflows, the last error in the queue is replaced with
error − 350, "Queue overflow" . Any time the queue overflows, the least
recent errors remain in the queue, and the most recent error is discarded.
The length of the Counter's error queue is 10 (9 positions for the error
messages, and 1 position for the "Queue overflow" error). Reading an error
from the head of the queue removes that error from the queue, and opens
a position at the tail of the queue for a new error, if one is subsequently
detected. When all errors have been read from the queue, further error
queries return +0, "No error" .
The error queue is cleared when any of the following events occur:
• Power-on.
Receipt of a *CLS command.
•
• The last item is read from the queue.
5-4 Programming Guide