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HP-IB Programming
Introduction to Programming the OLA
The Error Queue
If a command or query cannot be processed successfully, an error
message is placed in the error queue. Error messages consist of the
error code and the error text.
The error queue is a FIFO queue (first in - first out). It can hold up
to 30 error messages. If the error queue is full, the message “-350
Queue overflow” is inserted as the last message.
To find out whether an error occurred, you can transmit the
“*ESR?” query and check the bits 2 – 5 of the Event Status register.
To read the error queue, you have to issue the “:SYST:ERR?”
query. You will receive the oldest error message stored in the queue.
This message is automatically removed from the queue. Thus, you
can clear the error queue by issuing the “:SYST:ERR?” query
repeatedly.
Some Notes about Programming and Syntax
Conventions
The following are a few points about the commands and queries
sent to the OLA.
Sending Messages to the OLA
• You can use either upper-case or lower-case characters. The
characters 00 to 09 and 0B to 1F (Hex) are converted to space
characters (20 Hex). Two or more spaces are compressed to one.
• You can send several commands in a single message. Each
command must be separated from the next one by a semicolon
(;).
• You terminate a message with a line feed character (LF), or any
character sent with End-Or-Identify (EOI). Upon detection of
EOI, a LF is inserted into the input queue.
• You can use any valid number/unit configuration. For example:
1500nm, 1.5um and 1.5e-6m are all equivalent.
If you don’t specify a unit, the command’s default unit is assumed.
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