VXI 3002 manual Error handling, Background errors, Foreground errors, Error queue

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.

3-40