R&S ZVL
Remote Control
Command Processing
Operating Manual 1303.6580.32-05
330
Command Processing
The block diagram below shows how GPIB bus commands are serviced in the instrument.
The individual components work independently and simultaneously. They communicate with each other by
means of so-called "messages".
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.
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.
