Error Queue - Keithley 2303 User Manual

7-18 Status Structure

Error queue

The error queue holds error and status messages. When an error or status event occurs, a mes-
sage that defines the error/status is placed in the error queue.
When a message is placed in the error queue, the error available (EAV) bit in the status byte
register is set. An error/status message is cleared from the error queue when it is read. The error
queue is considered cleared when it is empty. An empty error queue clears the EAV bit in the
status byte register.
The error queue holds up to 10 error/status messages. The commands to read the error queue
are listed in Table 7-6. When you read a single message in the error queue, the "oldest" message
is read and then removed from the queue. If the queue becomes full, the message "350, 'queue
overflow'" will occupy the last memory location. On power-up, the error queue is empty. When
empty, the message "0, No Error" is placed in the queue.
Messages in the error queue are preceded by a code number. Negative (-) numbers are used
for SCPI defined messages, and positive (+) numbers are used for Keithley defined messages.
The messages are listed in Appendix B.
On power-up, all error messages are enabled and will go into the error queue as they occur.
Status messages are not enabled and will not go into the queue. As listed in Table 7-7, there are
commands to enable and/or disable messages. For these commands, the <list> parameter is used
to specify which messages to enable or disable. The messages are specified by their codes. The
following examples show various forms for using the <list> parameter.
<list>
When you enable messages, messages not specified in the list are disabled. When you disable
messages, each listed message is removed from the enabled list.
= (-110)
= (-110:-222)
= (-110:-222, -220)
Single message
Range of messages (-110 through -222)
Range entry and single entry (separated by a comma)