R&S
®
CMW 500 Remote Control
Command Processing
Operating Manual 1202.3986.32 – 03 100
communicate with each other by means of so-called "messages".
5.5.1 Input Unit
The input unit receives commands character by character from the controller and
collects them in the input buffer. The input unit sends a message to the command
recognition as soon as the input buffer is full or as soon as it receives a delimiter,
<PROGRAM MESSAGE TERMINATOR>, as defined in IEEE 488.2, or the interface
message DCL.
If the input buffer is full, the message data traffic is stopped and the data received up to
then is processed. Subsequently the traffic is continued. If, however, the buffer is not
yet full when receiving the delimiter, the input unit can already receive the next
command during command recognition and execution. The receipt of a DCL clears the
input buffer and immediately initiates a message to the command recognition.
5.5.2 Command Recognition
The command recognition stage analyzes the data received from the input unit. It
proceeds in the order in which it receives the data. Only a DCL is serviced with priority,
e.g. a GET (Group Execute Trigger) is only executed after the commands received
before. Each recognized command is immediately transferred to the data set but not
executed immediately.
The command recognition detects syntax errors in the commands and transfers them
to the status reporting system. The rest of a command line after a syntax error is still
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