Keithley 2182, User Manual, Page: 192 / 339

11-18 Remote Operation
Queues
The Model 2182 uses two queues, which are first-in, first-out (FIFO) registers:
• Output Queue – Used to hold reading and response messages.
• Error Queue – Used to hold error and status messages.
The Model 2182 status model ( Figure 11-4 ) shows how the two queues are structured with
the other registers.
Output queue
The output queue holds data that pertains to the normal operation of the instrument. For
example, when a query command is sent, the response message is placed in the Output Queue.
When data is placed in the Output Queue, the Message Available (MAV) bit in the Status Byte
Register sets. A data message is cleared from the Output Queue when it is read. The Output
Queue is considered cleared when it is empty. An empty Output Queue clears the MAV bit in
the Status Byte Register.
Read a message from the Output Queue by addressing the Model 2182 to talk after the
appropriate query is sent.
Error queue
The Error Queue holds error and status messages. When an error or status event occurs, a
message that defines the error/status is placed in the Error Queue. This queue will hold up to 10
messages.
When a message is placed in the Error Queue, the Error Available (EAV) bit in the Status Byte
Register is set. An error message is cleared from the Error/Status 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. Read an error message from the Error Queue by sending either of
the following SCPI query commands and then addressing the Model 2182 to talk:
• :SYSTem:ERRor?
• :STATus:QUEue?