Pressure Systems 9816, 98RK Chapter Programming and Operation Commands & Responses, Introduction

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

Chapter 3

Programming and Operation

3.1Commands & Responses

3.1.1Introduction

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-1chassis. 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-1chassis 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-1chassis).

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.

3.1.2TCP/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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