Queues; Output Queue; Error Queue - Keithley 2651A Reference Manual

Model 2651A High Power System SourceMeter® Instrument Reference Manual

Queues

The Model 2651A uses two queues, which are first-in, first-out (FIFO) queues:
•
Output queue: Used to hold response messages.
•
Error queue: Used to hold error and status messages (see
The Model 2651A status model
are structured with the other registers.

Output queue

All interfaces share the same output queue. The output queue sets the message available (MAV) bits
in the status model. The data in the output queue clears if the mode changes to local mode.
You must save the data from the output queue while the instrument is communicating with the remote
command interface. All data in the output queue is cleared when the instrument returns to local mode.

Error queue

The error queue holds error and status messages. When an error or status event occurs, a message
that defines the error or 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 or 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 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. When the instrument
power is turned on, the error queue is initially empty. If there are problems detected when the
instrument power is turned on, entries will be placed in the queue. When empty, the error number 0
and "No Error" is placed in the queue.
Messages in the error queue include a code number, message text, severity, and TSP-Link
number. The messages are listed in
Error queue commands
Error queue command
errorqueue.clear()
errorqueue.count
errorCode, message,
severity, errorNode =
errorqueue.next()
2651A-901-01 Rev. A / March 2011
(Status model overview
NOTE
Error summary (on page 8-1).
Description
Clear error queue of all errors.
Number of messages in the error/event queue.
Request error code, text message, severity, and TSP-Link node
number.
Appendix E: Status model
Error summary list
(on page E-4)) shows how the two queues
(on page 8-2)).
®
node
E-25