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Measurement Specialties Inc. NetScanner System (9016, 9021, & 9022) User’s Manual

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Chapter 3

Programming and Operation

3.1 Commands & Responses

3.1.1 Introduction

This chapter describes all commands a host computer program may send to a NetScanner

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System Intelligent Pressure Scanner module, as well as the data or status responses returned by

the module. Most applications require a working knowledge of only a small number of these

commands. Most commands apply to all pressure scanner models. However, some apply only

to specific models as will be noted in the command description (e.g., Model 9016 or Model 9022).

Models 9016, 9021, and 9022 (stand alone scanner modules), have an Ethernet interface, and use

layered TCP/IP or UDP/IP transmission protocols to communicate with a host computer. All

commands/responses to/from NetScanner

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System modules are embedded in the data fields of

either a TCP or UDP packet header. In turn, these packets are themselves embedded in the data

field of an IP packet header, which is embedded in the data field of an Ethernet packet header.

Thus, the term layered protocols.

3.1.1.1 TCP/UDP/IP Protocols

Both TCP/IP and UDP/IP protocols are a well-established set of rules for communicating over a

network (LAN, intranet, or internet), and are independent of the network’s physical medium. All

the modules use the TCP/IP protocols for most commands and responses since the TCP layer

provides a robust error detection and correction mechanism. TCP/IP requires a formal

connection be established between host and module. The simpler UDP layer, requiring no formal

connection, is utilized for a subset of commands and query responses.

Using the underlying basic IP protocol, the host computer and interconnected modules are all

“peers” that can communicate equally. Each “peer” must have its own unique “logical” IP

Address (as well as its own unique “physical” Ethernet Address) to be directly addressed. Any

“peer” may initiate transmissions without permission from the receiver. In the NetScanner

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System implementation, the host computer is normally a client and generally initiates most

transmissions by sending commands to the modules, which are normally servers. However, a

module can initiate its own transmissions in some operating modes (e.g., the hardware-triggered

or free-run autonomous host streams generated by the Configure/Control Autonomous Host

Streams (‘c’) command).

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Pressure Systems 9022 Manuel d'utilisateur Page 34