6-6
IM DLM4038-17EN
6.5 Output and Error Queues
Output Queue
The output queue stores query response messages. For example, if you send a
:WAVeform:SEND?
command, which requests for the transmission of acquired data, the data is stored in the output
queue until it is read.
As shown below, data is stored in order and read from the oldest message first. The output queue is
cleared when:
• A new message is received from the controller.
• A deadlock occurs (see page 4-2).
• A device clear command (DCL or SDC) is received.
• The DLM4000 is turned off and then back on.
The
*CLS
command does not clear the output queue. You can determine whether or not the output
queue is empty by checking the status byte bit 4 (MAV).
D1
D2
D1
D2
D1
Error Queue
When an error occurs, the error queue stores the error number and message. For example, if the
DLM4000 receives an incorrect program message from the controller, the error number (113) and
the error message (“Undefined header”) are stored in the error queue when the DLM4000 displays
the error message.
You can use the
:STATus:ERRor?
query to read the contents of the error queue. Like the output
queue, the messages in the error queue are read from the oldest one first.
If the error queue overflows, the last message is replaced with the following message: 350, “Queue
overflow”
The error queue is cleared when:
• A
*CLS
command is received.
• The DLM4000 is turned off and then back on.
You can determine whether or not the error queue is empty by checking bit 2 in the status byte (EAV).