VXI 3002 - Manual (Page 70)

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Error messages
Error handling
Error messages are divided into four groups:
(1) Background errors - represent a condition of the instrument.
(2) Foreground errors - generally caused by the user.
(3) IEEE 488.2 errors - generated by incorrect programming.
(4) Fatal errors - caused by failure associated with the main RAM or the
PROM. These errors may or may not be displayed according
to the severity of the failure or corruption.
Background errors:
These are generated due to an incorrect operating condition within the instrument. These errors are
generated automatically to warn the operator. For example if the reverse power protection circuit
should trip error 500 (RPP tripped) will be placed in the error queue. Background errors are listed
in Table 3-3.
Foreground errors:
These are typically generated when an entered parameter value is outside the valid range or for
some other invalid operation. For example trying to set the carrier frequency above or below the
specified range will put error 100 (Carrier limit) into the error queue. Foreground errors are listed
in Table 3-4.
Error queue
When an error occurs the error number is put into the error queue. The error at the head of the
queue is only cleared by the ERROR? query, which returns that error, or by the *CLS command
which clears the whole error queue. IEEE 488.2 errors are listed in Table 3-5.
The queue holds a maximum of 64 error message error numbers. If an error occurs while the queue
is full the last error number is replaced with 399 to indicate that the queue is full. The ERROR?
query returns a value of 399 for queue full and 0 for queue empty.
When an error number is written into the queue, a bit (<erb>) in the status byte register is set, and
an appropriate bit in the standard event register is also set (one of <cme>, <exe>, <dde> or <qye>).
These errors will also generate a VXI controller interrupt for the event 'Request True' if the
appropriate interface settings have been set up. Many background errors are also reported in the
Hardware and Coupling Status Registers.