Annexes
R&S
®
CMW500
270
User Manual 1173.9463.02 ─ 02
For instruments with display optional (R&S CMW-B620A).
8.1.2 LAN Interface
To be integrated in a LAN, the instrument is equipped with a LAN interface, consisting of
a RJ-45 connector, a network interface card and protocols. The network interface card
supports IEEE 802.3 for a 10 Mbps Ethernet and IEEE 802.3u for a 100 Mbps Ethernet.
Instrument access is possible via the
. It is usually achieved from high level programming platforms by
using VISA as an intermediate abstraction layer. VISA encapsulates the low level function
calls and thus makes the transport interface transparent for the user. The necessary VISA
library is available as a separate product. For details contact your local R&S sales rep-
resentative.
8.1.2.1
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 ser-
vices 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. An example is shown in the figure below.
Fig. 8-1: Example of OSI layers (VXI-11 protocol)
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:
Interfaces and Connectors
