ICS ELECTRONICS 9099, Инструкция по эксплуатации

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A-13
A2
COMM_Timeout can be set to a low period like 3-5 minutes for quick socket
recovery 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 hours to avoid prematurely closing the socket when not
communicating with the unit. Hard wired systems are pretty dependable and
the user can safely extend COMM_Timeout to several hours or to even days.
Do not set COMM_Timeout to 0, which disables the timeout, unless there is a
way to physically reset the unit 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
closing sockets. To overcome this problem, ICS's VXI-11 Interfaces 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, ICS's
VXI-11.3 Instruments 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 a Reverse Interrupt Channel to alert the application
that an event has occurred and/or that the device needs service. One method
of handling this 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. During the setup, the instrument is given
the PC's IP address and initial port number. An RPC service is installed in the
PC. The creation of the RPC service will provides 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 the user 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 ICS’s Application
Note AB80-4 for more detailed information on RPC SRQ programming and
interrupt handling.