Output And Error Queues - YOKOGAWA WT1800 User Manual

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 waveform 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 in the following cases.
• 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 instrument is turned off and then back on.
The *CLS command does not clear the output queue. You can determine whether the output queue
is empty by checking bit 4 (MAV) in the status byte.
Error Queue
When an error occurs, the error queue stores the error number and message. For example, if the
instrument 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 instrument displays
the error message.
You can use the :STATus:ERRor? query to read the contents of the error queue. Like those in 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 in the following cases.
• A *CLS command is received.
• The instrument is turned off and then back on.
You can determine whether the error queue is empty by checking bit 2 (EAV) in the status byte.
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IM WT1801-17EN