ICS ELECTRONICS 9099, Instruction Manual

Page: 123 / 178

A-11
A2
A2 VXI-11 PROTOCOL AND EXAMPLE PROGRAM
This Appendix describes the VXI-11 Protocol, its applicability to ICS's 80xx
series Interfaces and includes a C language VISA program.
The VXI-11 protocol uses Remote Procedure Calls (RPC) that provides an
invisible communication medium allowing the developer to concentrate on his
program. Remote Procedure Calls are requests sent from a client, such as the
user's program, to a remote server to carry out the instruction. Responses are re-
turned to every RPC so the client can be sure the request was accomplished.
Windows users can use VXI-11 compliant VISA libraries like those from
National Instruments or Agilent that include the capability to make RPC calls
VXI-11.3 Instruments like ICS's 80xx Interfaces. That way, VXI-11.3 Instru-
ments can be programmed with familiar graphical applications like LabView
or VEE. Both applications call a VISA layer that makes VXI-11 calls over the
TCP/IP network. C and Visual Basic programs can be written with SICL or
VISA calls to control VXI-11.3 Instruments.
Linux, UNIX or any other flavor of UNIX like SunOS, IBM-AIX, HP-UX, or
Apple's OS X, can communicate with the VXI-11.3 Instruments through either
with RPC over TCP/IP. The VXI-11 Specification, available at http://www.
vxibus.org or from ICS Electronic's website, includes a RPCgen header file
listing that can be used to generate RPC calls. RPC calls can be used with
virtually any operating system that has TCP/IP communication capability and a
RPCgen utility. Refer to ICS's Application Notes APB80-3 for more informa-
tion about RPC Programming.
Java users can write RPC applications that run on nearly all computer platforms
with the Java library from jGPIBenet project on SourceForge. Refer to ICS's
Application Notes for detailed information on programming VXI-11 devices.
A2.1 Sockets, Channels and Links
VXI-11 devices, like ICS's 80xx and 90xx series Interfaces, use a socket con-
nection for bi-directional communication with a client which is the application
program running in a computer. Sockets maybe thought of as pipes that sup-
port multiple links. After the socket connection is established, the client must
establish a link to the instrument to communicate with it.
ICS's 80xx and 90xx series Interfaces have 15 sockets for connection with
multiple clients at a time and a 16th socket for UDP communication. UDP
protocol may be used initially when the client scans for a VXI-11 server. The