VXI-11(网络设备)协议学习

›VXI-11 Concept

›VMEbus Extensions for Instrumentation TCP/IP Instrument Protocol Specification VXI-11, Revision 1.0 is authored by the VXIbus Consortium, Inc. and its sponsor members:

–GenRad, Inc.

–Hewlett-Packard Co.

–National Instruments, Corp.

–Racal Instruments, Inc.

–Tektronix, Inc.

–Wavetek, Inc.

›VXI-11 Family

–VXI-11.1TCP/IP-VXIbus Interface Specification

–VXI-11.2TCP/IP-IEEE 488.1 Interface Specification

–VXI-11.3TCP/IP-IEEE 488.2 Instrument Interface Specification

 

Network Instrument Protocol

›The network instrument protocol uses the ONC remote procedure call (RPC) model. Conceptually, this model allows one application (typically called the client) to call procedures in a remote application (typically called the server) as if the remote procedures were local.

›This specification uses ONC/RPC for defining thenetwork instrumentmessages which are passed over the network, but does not require that these RPCs be provided as the application interface. The ONC/RPC interface may,  however, be used by a device designer as a matter of convenience.

 

Network Instrument Protocol

 

Protocol Foundations

The network instrument protocol is an application layer protocol designed for controller to device

communication using a paradigm similar to communication with IEEE 488 devices.

The networkinstrument protocol is built on an industry-standard protocol stack, allowing instrumentation and controllers to communicate over existing networks.

The following sections work from the bottom of the protocol stack upward, describing the protocol stack requirements of controllers or devices which implement thenetwork instrumentprotocol.

 

Protocol Stack Summary

 

Network Instrument Messages (RPCs)

 

Example:create_link

›The create_link RPC creates a new link. This link is identified on subsequent RPCs by thelidreturned

›from the network instrument server.

›struct Create_LinkParms {

›long clientId; /* implementation specific value.*/

›bool lockDevice; /* attempt to lock the device */

›unsigned long lock_timeout; /* time to wait on a lock */

›string device<>; /* name of device */

›};

›struct Create_LinkResp {

›Device_ErrorCode error;

›Device_Link lid;

›unsigned short abortPort; /* for the abort RPC */

›unsigned long maxRecvSize; /* specifies max data size in bytes

›device will accept on a write */

›};

›Create_LinkResp create_link(Create_LinkParms) = 10;

›RULE B.6.3:

›To successfully complete a create_linkRPC, anetwork instrumentserver SHALL:

›1. If lockDevice is set to true, acquire the lock for the device.

›2. Return in lid a link identifier to be used with future calls. The value oflidSHALLbe unique for

›all currently active links within a network instrument server.

›3. Return in maxRecvSize the size of the largestdataparameter thenetwork instrument server can

›accept in a device_write RPC. This valueSHALLbe at least 1024.

›4. Return in asyncPort the port number for asynchronous RPCs. Seedevice_abort.

›5. Return with error set to 0, no error, to indicate successful completion.

›The device parameter is a string which identifies the device for communications. See the document(s)

›referred to in section A.6, Related Documents, for definitions of this string.

 

 

Demo

 

Port Map Register

 

›Port Map look up (GetPort Call)

Port Map look up (GetPort Reply)

Create Link Request

Create Link Response

 

Device Write Request

 

Device Write Response

 

›Device Read Request

 

›Device Read Response