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R&S ZVL
Interfaces and Connectors
Rear Panel Connectors
Operating Manual 1303.6580.32-05
591
Command QuickBASIC
command
Effect on the instrument
PPC
(Parallel Poll
Configure)
IBPPC (device%,
data%)
Configures the instrument for parallel poll. Additionally, the QuickBASIC command
executes PPE/PPD.
SDC
(Selected Device
Clear)
IBCLR (device%)
Aborts the processing of the commands just received and sets the command
processing software to a defined initial state. Does not change the instrument setting.
Instrument Messages
Instrument messages (commands) are transferred on the data lines of the GPIB bus while the
ATN
line is
not active. ASCII code is used.
Structure and syntax of the instrument messages are described the SCPI Reference chapter. The chapter
also provides a detailed description of all messages implemented by the analyzers.
VXI-11 Protocol
The VXI–11 standard is based on the RPC protocol which in turn relies on TCP/IP as the
network/transport layer. The TCP/IP network protocol and the associated network services are pre-
configured. TCP/IP ensures connection–oriented communication, where the order of the exchanged
messages is adhered to and interrupted links are identified. With this protocol, messages cannot be lost.
Remote control of an instrument via a network is based on standardized protocols which follow the OSI
reference model (see Fig. below).
Based on TCP/UDP, messages between the controller and the instrument are exchanged via open
network computing (ONC) – remote procedure calls (RPC). With XDR (VXI–11), legal RPC messages are
known as VXI–11 standard. Based on this standard, messages are exchanged between the controller and
the instrument. The messages are identical with SCPI commands. They can be organized in four groups:
•
Program messages (control command to the instrument)
•
Response messages (values returned by the instrument)
•
Service request (spontaneous queries of the instrument)
•
Low–level control messages (interface messages)
A VXI–11 link between a controller and an instrument uses three channels: core, abort and interrupt