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Chapter 3, Programming and operation 3.1 commands & responses – Pressure Systems 98RK-1 User Manual

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Pressure Systems, Inc. 98RK-1 & 9816 User’s Manual©

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www.PressureSystems.com



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 each of the
NetScanner

System Intelligent Pressure Scanner modules (Model 9816) that are connected

to the various slots of the 98RK-1 Scanner Interface Rack chassis, as well as the data or
status responses returned by these modules. Some of the commands are similar to those for
other NetScanner

System models (e.g., 903x, 9016/9116 or 9021/9022) that may be

externally attached to the 98RK-1 chassis. However, refer to their appropriate users’ manuals
since some commands are model-specific. Most applications require working knowledge of only
a small number of commands.

Each internal Model 9816 pressure scanner module (mounted in 98RK-1 chassis slots) has an
Ethernet interface and uses layered TCP/UDP/IP transmission protocols to communicate with a
host computer. These same protocols (and Ethernet interface) are also used for any externally-
connected scanner or standard/calibrator modules (connected to the 98RK-1 chassis rear
connectors). These modules are all “networked” together (with a host computer) via the 12-port
Ethernet gigabit switch (inside the 98RK-1 chassis).

All commands/responses to and from NetScanner

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.

3.1.2 TCP/UDP/IP Protocols

TCP/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. The Model
9816
uses the TCP/IP protocols for most commands and responses since the TCP layer
provides a robust error detection and correction mechanism, but requires the establishment of a
formal connection between host and module. The simpler UDP layer, requiring no formal
connection, is utilized for a few simple commands and a query response.

Using the underlying basic IP protocol, the host computer and interconnected modules are all
“peers” that can all communicate equally. Each “peer” must have a 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 NetScanner

System

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

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