Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 447 / 813

R&S
®
ZVA/ZVB/ZVT Command Processing
1145.1084.12 5.15 E-1
commands. This means that new commands can already be serviced while the hardware is still being
set ("overlapping execution").
Data Set and Instrument Hardware
The expression "instrument hardware" denotes the part of the instrument fulfilling the actual instrument
function – signal generation, measurement etc. The controller is not included. The data set is a detailed
software reproduction of the instrument hardware.
GPIB bus setting commands lead to an alteration in the data set. The data set management enters the
new values (e.g. frequency) into the data set, however, it only passes them on to the hardware when
requested by the command recognition. As this is only ever effected at the end of a command line, the
order of the setting commands in the command line is not relevant.
The commands are only checked for their compatibility among each other and with the instrument
hardware immediately before they are transmitted to the instrument hardware. If the detection is made
that execution is not possible, an "execution error" is signalled to the status reporting system. All
alterations of the data set are canceled, the instrument hardware is not reset. Due to the delayed
checking and hardware setting, however, impermissible instrument states can be set for a short period
of time within one command line without this leading to an error message (example: simultaneous
activation of FM and PM). At the end of the command line, however, a permissible instrument state
must have been reached again.
Before passing on the data to the hardware, the settling bit in the
STATus:OPERation
register is set
(cf. section STATus:OPERation Register ). The hardware executes the settings and resets the bit again
as soon as the new state has settled. This fact can be used to synchronize command servicing.
GPIB bus queries induce the data set management to send the desired data to the output unit.
Status Reporting System
The status reporting system collects information on the instrument state and makes it available to the
output unit on request. The exact structure and function are described in section
Status Reporting
System.
Output Unit
The output unit collects the information requested by the controller, which it receives from the data set
management. It processes it according to the SCPI rules and makes it available in the output buffer. If
the information requested is longer, it is made available "in portions" without this being recognized by
the controller.
If the instrument is addressed as a talker without the output buffer containing data or awaiting data from
the data set management, the output unit sends the error message "Query UNTERMINATED" to the
status reporting system. No data is sent on the GPIB bus, the controller waits until it has reached its
time limit. This behavior is specified by SCPI.
Command Sequence and Command Synchronization
What was said above makes clear that overlapping execution is possible in principle for all commands.
Equally, setting commands within one command line are not absolutely serviced in the order in which