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3.1 Messages
Response message unit format
The format of a program message unit is shown below.
<Response header>
Space
<Response header>
A response header sometimes precedes the response
data. Response data must be separated from the
header by a space. For details, refer to page 3-4.
<Response data>
Response data is used to define a response. If
multiple items of response data are used, they must be
separated by a "
,
" (comma). For details, refer to page
3-5.
Example
100.00E-03<RMT>
:DISPLAY:FORMAT WAVE<RMT>
Data
If a program message contains more than one query,
responses are made in the same order as the queries.
Normally, each query returns only one response
message unit, but there are some queries which return
more than one response message unit. The first
response message unit always responds to the first
query, but it is not always true that the 'n' th unit
always responds to the 'n' th query. Therefore, if you
want to make sure that a response is made to each
query, the program message must be divided up into
individual messages.
Points to Note concerning Message Transmission
• It is always possible to send a program message if
the previous message which was sent did not
contain any queries.
• If the previous message contained a query, it is not
possible to send another program message until a
response message has been received. An error will
occur if a program message is sent before a
response message has been received in its entirety.
A response message which has not been received
will be discarded.
• If an attempt is made by the controller to receive a
response message, even if there it no response
message, an error will occur. An error will also
occur if the controller makes an attempt to receive a
response message before transmission of a
program message has been completed.
3-2
,
<Response data>
Header
Data
• If a program message of more than one unit is sent
and some of the units are incomplete, this
instrument receives program message units which
the instrument thinks complete and attempts to
execute them. However, these attempts may not
always be successful and a response may not
always be returned, even if the program message
contains queries.
Deadlock
This instrument has a buffer memory in which both
program and response messages of 1024 bytes or
more can be stored. (The number of bytes available
will vary depending on the operating state of the
instrument.) If the transmission and reception buffer
memories become full at the same time, the instrument
will not be able to continue the communication
operation. This state is called deadlock. In this case,
operation can be resumed by discarding the response
message.
No dead lock will occur, if the size of the program
message including the PMT is kept below 1024 bytes.
Furthermore, no deadlock will occur if the program
message does not contain a query.
IM 253710-11E
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