Appendix E: Status model
2606B System SourceMeter® Instrument Reference Manual
E-2
2606B-901-01 Rev. B / May 2018
Queues
The 2606B uses queues to store messages. The queues include:
•
Command queue: Holds commands that are available for execution.
•
Output queue: Holds response messages.
•
Error queue: Holds error and status messages.
When a queue contains data, it sets the condition bit for that queue in one of the registers. The
condition bits are:
•
Command queue: CAV in the Operation Status Remote Summary Register
•
Output queue: MAV in the Status Byte Register
•
Error queue: EAV in the Status Byte Register
The CAV, MAV, and EAV bits in the registers are cleared when the queue is empty. Queues empty
when:
•
Commands are executed
•
Errors are read from the error queue
•
Response messages are read from the instrument
All 2606B queues are first-in, first-out (FIFO).
The
(on page E-4) section shows how the queues are structured with the
other registers.
Output queue
Response messages, such as those generated from print commands, are placed in the output queue.
All remote command interfaces share the same output queue.
The output queue sets the message available (MAV) bit in the status model.
The data in the output queue is cleared by the
*CLS
command.
Error queue
The error queue holds error and status messages. As programming errors and status messages
occur, a message that defines the error or status is placed in the error queue.
An error or status message is cleared from the error queue when it is read. You can also clear the
error queue by sending the command
errorqueue.clear()
. An empty error queue clears the error
available (EAV) bit in the Status Byte Register.
Messages in the error queue include a code number, message text, severity, and TSP-Link
®
node
number. See
(on page 8-2) for a list of the messages.
When you read a single message from the error queue, the oldest message is read. If you attempt to
read the error queue when it is empty, the error number 0 and “No Error” is returned.
The commands that can be used to control the error queue are listed below.
Error queue commands
Error queue command
Description
errorqueue.clear()
Clear error queue of all errors.
errorqueue.count
Number of messages in the error/event queue.
errorCode, message,
severity, errorNode =
errorqueue.next()
Request error code, text message, severity, and TSP-Link node
number.
