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14-6

IM 2558A-01EN

14.5 Output and Error Queues

Output Queue

The output queue stores query response messages. For example, if you send a

:SOURce:READ?

command, which requests for the transmission of voltage or current output value, the response

message is stored in the output queue until it is read.

As shown below, error messages are stored in order and read from the oldest message first. The

output queue is cleared in the following cases.

• When a new message is received from the controller.

• When a deadlock occurs (see section 12.1).

• When a device clear command (DCL or SDC) is received.

• When the 2558A is restarted.

The

*CLS

command does not clear the output queue. You can determine whether or not the output

queue is empty by checking bit 4 (MAV) in the status byte.

D1 D2

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 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.

• When a

*CLS

command is received.

• When the 2558A is restarted.

You can determine whether or not the error queue is empty by checking bit 2 (EAV) in the status byte.

YOKOGAWA 2558A User Manual

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