Error Available Bit (Error Or Event Queue; Questionable Summary Bit (Questionable Event Register - Keithley 708B Reference Manual

Models 707B and 708B Switching Matrix Reference Manual

Error available bit (Error or Event queue)

The summary bit of the Error or Event queue provides enabled summary information to Bit 2 (EAV) of
the status byte.
The Error Available Bit (EAV) is set when a message defining an error (or status) is placed in the
Error or Event queue. The Error or Event queue is one of the two Switching Matrix queues associated
with the status model. The other queue sets the Message available bit (Output queue)). Both queues
are first-in, first-out (FIFO) queues. The Error queue holds error and status messages. The status
model shows how these queues are structured with regard to the other registers.
The following sequence outlines typical events associated with this queue:
1. When an error or status event occurs, a message defining the error (or status) is placed in the
Error queue.
2. The Error Available (EAV) bit in the Status Byte Register is set.
3. Through programming, the error (or status) message is read. This clears the error (or status) from
the Error Queue. The Error queue is considered cleared when it is empty.
4. An empty Error queue clears the EAV bit in the Status Byte Register.
The commands to control the Error queue are listed below. When you read a single message in the
Error queue, the oldest message is read and then removed from the queue. On power-up, the Error
queue is initially empty. If there are problems detected during power-on, entries will be placed in the
queue. If no problems are detected, the error number 0 and "No Error" will be returned.
Error queue command
errorqueue.clear()
errorqueue.count
errorqueue.next()
Messages in the Error queue include a code number, message text, severity, and TSP-Link node
number. For example, the following commands request the next complete error information from the
error queue and displays the code, message, severity and node of the next error:
errorcode, message, severity, errornode = errorqueue.next()
print(errorcode, message, severity, errornode)
The error messages, as well as error numbers, are listed in the Error summary list.

Questionable summary bit (Questionable event register)

The summary bit of the questionable event register provides enabled summary information to Bit 3
(QSB) of the status byte.
707B-901-01 Rev. A / August 2010
Description
Clear error queue of all errors.
Number of messages in the error/event queue.
Request error message.
Appendix C: Status model
C-7