A-13
A2
locks) become available to another client.
The 80xx’s COMM_Timeout can be set to a low period like 3-5 minutes when
the user is first debugging a program and tends to breakout of the program
without properly closing the sockets. Later, with a finished program, extend
the time to 10 minutes or even hours to avoid prematurely closing the socket
while you are not communicating with the 80xx. Hard wired systems are pretty
dependable and you can extend the 80xx’s COMM_Timeout to several hours
or even days. Do not set it to 0, which disables the timeout, unless you have a
way to physically reset the 80xx if it runs out of resources. A temporary setting
of 0 is useful when debugging third party software.
A2.2 Auto-disconnect
Agilent Instruments have a non-standard behavior that closes (aborts) a socket
whenever the link count goes to zero. This behavior is non-standard because the
VXI-11 Specification and RPC only expect the client to close a socket. Some
Agilent IO library programs rapidly open and close sockets when attempting
to discover instruments or perform other functions. This quickly exhausts all
of a VXI-11 device's resources because of the operating system's lag in clos-
ing sockets. To overcome this problem, ICS's 80xx series Interface have a
Auto-disconnect function that can be enabled for use with Agilent IO libraries
programs that expect this behavior.
A2.3 Service Requests (SRQs)
VXI-11 Instruments can generate Service Requests in a fashion similar to the
SRQ generation in a GPIB device. Instead of asserting the GPIB SRQ line,
VXI-11.3 Instruments, like the 80xx, generate a Service Request message,
device_intr_SRQ,
when the RQS bit in the Status Byte Register becomes true.
Service Requests (SRQs) are sent through an Interrupt Channel to alert the
'client' that an event has occurred and/or that the device needs service. One
method is for the user to set up a separate task in the program that can receive
the message with the id key string (handle) and set a flag. The task will be a
one-way RPC service that only has to receive a message and should not reply
to the VXI-11 Interface. You need to provide the 80xx with the IP address and
initial port number of the PC. You will also need to install or activate the RPC
service in your computer. The creation of the RPC service will provide you
the port number since the RPC handler will establish the TCP listening socket.
The IP address can be obtained through a socket call, but it does require you to
know which NIC to use (remember that a PC can have multiple Ethernet NIC
ports) which may require a configuration setup for the application. Refer to