Specifications

SLAA137A
MSP430 Internet Connectivity 3
1 Introduction
While known for its use in PC networks, the ethernet also offers a robust, well-understood and
reasonably priced technology for networking applications beyond the desktop computer. The
goal of this design is to show how easy it is to implement a TCP/IP stack as well as an ethernet
interface for the MSP430. It provides both a source code for the programmer as well as
schematics for the design engineer.
It is advantageous if the reader of this application report has a general knowledge of TCP/IP
networks and their related communication protocols. Section 2 contains some very basic
information about the protocols used. For more detailed information, additional sources of
information are mentioned. Sections 3 and 4 present both the hardware and software parts of
the demonstration board featured in this application report.
Using the knowledge of this demonstration board, many applications are imaginable. Think of
home automation, utility meters, appliances, security systems, card readers and building
controls that can be easily controlled using either special front-end software or a comfortable
Internet browser from anywhere around the world. The big advantage of an HTTP server in an
embedded environment is that the web browser manages the whole user interface. The
visualizing of information can be done simply by sending ASCII strings (HTML source) to the
client and therefore minimal resources are required.
2 Important Protocol Basics
It is common to describe protocol stacks with a layered model. Each of these layers provides its
own functions to upper level protocols and also uses help of lower level protocols to provide its
services. The operational details of the lower layers are hidden from the higher layers. That
simplifies both software design and maintenance. For example, a new transport layer using a
different communication medium can be created, and it is not necessary to change the code of
the upper layers. The reference model commonly used for describing the Internet architecture is
a subset of the ISO/OSI seven-layer model. Figure 1 shows the relationship between these
models and Table 1 the function of the different layers in the Internet reference model.
Application Layer
Presentation Layer
Session Layer
Transport Layer
Data Link Layer
Network Layer
Physical Layer
Application Layer
Transport Layer
Internet Layer
Network Layer
Figure 1. ISO/OSI vs Internet Reference Model