6-12 GPIB Operation
Response messages
A response message is the message sent by the instrument to the computer in response to a
query command program message.
Sending a response message
After sending a query command, the response message is placed in the output queue. When
the power supply is then addressed to talk, the response message is sent from the output queue
to the computer.
Multiple response messages
If you send more than one query command in the same program message (see “Multiple com-
mand messages”), the multiple response messages for all the queries are sent to the computer
when the power supply is addressed to talk. The responses are sent in the order the query com-
mands were sent and are separated by semicolons (;). Items within the same query are separated
by commas (,). The following example shows the response message for a program message that
contains four single item query commands:
0; 1; 1; 0
Response message terminator (RMT)
Each response is terminated with an LF (line feed) and EOI (end or identify). The following
example shows how a multiple response message is terminated:
0; 1; 1; 0; <RMT>
Message exchange protocol
Two rules summarize the message exchange protocol:
Rule 1: You must always tell the power supply what to send to the computer.
The following two steps must always be performed to send information from the instrument
to the computer:
1. Send the appropriate query command(s) in a program message.
2. Address the power supply to talk.
Rule 2: The complete response message must be received by the computer before another
program message can be sent to the power supply.
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