SCPI Introduction
Copyright © Itech Electronic Co., Ltd.
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end of each message.
Command execution rules
⚫
Commands execute in the order that they are presented in the program
message.
⚫
An invalid command generates an error and, of course, is not executed.
⚫
Valid commands that precede an invalid command in a multiple command
program message are executed.
⚫
Valid commands that follow an invalid command in a multiple command
program message are ignored.
1.4 Response Data Type
Character strings returned by query statements may take either of the following
forms, depending on the length of the returned string:
⚫
<CRD>
: character response data. Permits the return of character strings.
⚫
<AARD>
: arbitrary ASCII response data. Permits the return of undelimited
7-bit ASCII. This data type has an implied message terminator.
⚫
<SRD>
: string response data. Returns string parameters enclosed in
double quotes.
⚫
<Block>
: arbitrary block data.
Response messages
A response message is the message sent by the instrument to the computer in
response to a query command.
Sending a response message
After sending a query command, the response message is placed in the Output
Queue. When the instrument 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, the
multiple response messages for all the queries is sent to the computer when
the instrument is addressed to talk. The responses are sent in the order that the
query commands 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:
