R&S NRP2, Руководство пользователя

Страница: 372 / 437

Remote control interfaces
R&S
®
NRP2
354 User Manual 1173.9157.02 ─ 03
Table 1-4: Communications channels of a VXI11 connection
Channel Meaning
Core All communications between client and server are handled via this channel, with the exception
of abort and interrupts.
Abort Since the commands in the core channel are serialized and therefore cannot be interrupted,
asynchronous abort commands must be handled via a separate, independent channel. This
channel has no other tasks.
Interrupt Service requests (SRQ) are signaled via this channel to the network instrument client. As this
channels is shared by all links, the client must determine which device has triggered the SRQ
by querying the status bytes (function device_readstb()) of all connected devices.
A.2.2 Connection setup
A socket connection is set up for each channel. All commands via the core or abort
channel contain an ID that is used to assign the command to a link. The interrupt channel,
which is also implemented using sockets, is shared by all links. Commands transmitted
via this channel do not contain a link ID. The setup is handled by the network instrument
client, which first requests the connections from the network instrument server's port-
mapper service at port 111. The portmapper subsequently activates the channel in the
R&S
NRP2 and tells the client at which ports channel services can be addressed. For
this reason, it is important that any firewalls or routers between the client and the
R&S
NRP2 enable free access from the controller to the R&S NRP2 (core and abort
channels) and vice versa (interrupt channel). As the ports for the channels are dynami-
cally assigned, reliable information regarding the port numbers used cannot be provided.
A.2.3 Remote control via VXI11
The following possibilities are suggested for remote-controlling the R&S NRP2 via VXI11:
●
The simplest way to create remote-control programs is by using a virtual instruments
software architecture (VISA) implementation and creating the remote-control pro-
grams under Visual Basic or C/C++. VISA implementations provide an application
programming interface (API) that offers all necessary functions. Knowledge about
VXI11 is helpful but not required. The VISA resource identifier used to identify a VXI11
device has the following format: TCPIP::<IP address>::INSTRThe IP address is
specified using the familiar dot notation (e.g. 89.10.65.59).
–
TCPIP::<IP address>::INSTR
The IP address is specified using the familiar dot notation (e.g. 89.10.65.59).
●
Annex C of the TCP/IP Instrument Protocol Specification VXI11 contains an RPCL
description of the protocol. The program rpcgen, which is included in any ONC RPC
distribution, is used to generate stubs. Stubs can be inserted into separate C pro-
grams, where the functions from the table below can be called like ordinary library
functions. This procedure requires RPC programming skills.
Ethernet