Rohde & Schwarz NRT 1080.9506.02/.62, Operating Manual

Page: 127 / 194

NRT Instrument Model and Command Processing
1080.9506.02 3.47 E-6
3.6 Instrument Model and Command Processing
The block diagram in figure Fig. 3-2 shows how IEC/IEEE-bus commands are serviced in the instru-
ment. The individual components work independently and simultaneously. They communicate with each
other by means of so-called "messages".
IEC bus
Input unit with
input buffer
Command
recognition
Data set
Instrument
hardware
IEC bus
Output unit with
output buffer
Status reporting
system
Fig. 3-2 Instrument model in the case of remote control by means of the IEC bus
3.6.1 Input Unit
The input unit receives commands character by character from the IEC bus 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 IEC/IEEE-bus traffic is stopped and the data received up to then are proc-
essed. Subsequently the IEC/IEEE-bus 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 recogni-
tion and execution. The receipt of a DCL clears the input buffer and immediately initiates a message to
the command recognition.
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