Casio EG-800U - Cassiopeia - Win CE 3.0 150 MHz Specifications download pdf (Page 19)

SLAA137A

MSP430 Internet Connectivity 19

Table 5. Compatible Communication Systems

Computer System / CPU Operating System, TCP/IP Stack

PC / Athlon™/ 1 GHz Windows 2000

PC / Athlon / 1 GHz Linux, kernel v 2.2.16

PC / Pentium™ / 233 MHz Windows 98

PC / 486DX2 / 66 MHz Windows 95

Apple™ Macintosh™ / 68030 / 50 MHz System 7.5, Open Transport™ 1.1.2

AT Amiga™ / 68030 / 50 MHz Kickstart 3.0, Miami 2.1

Cassiopeia™ / MIPS / 150 MHz Windows CE 3.0

The main limitations of the protocol specifications that were made are:

• Only one TCP session possible at one time

• No reassembling of fragmented incoming IP frames

• No buffering of TCP segments which are delivered out-of-order

• No checksum checking of incoming data

• No support for IP type-of-service (TOS) and security options

• Ignoring of any TCP options

Compatibility is achieved by implementing only the important parts of the protocol specifications,

but also is due to the tolerance of the other TCPs. This solution needs about 4.2KB of flash

EEPROM as program memory, 100 bytes of flash EEPROM as memory for storing constants,

and about 700 bytes of RAM.

The maximum transfer speed of the module cannot be defined exactly, as it largely depends on

the other TCP. Normally, a TCP that fully implements the protocol specification is able to receive

and buffer more than one segment at a time. Because the MSP430 has a relatively small

amount of memory compared with, for example, personal computers, it can maintain only one

receive and one transmit buffer. It needs to wait for an acknowledgement from the other TCP

before the overwriting of buffer contents is allowed and new data can be exchanged. Because of

the round-trip time (RTT) of packets sent over the Internet and the delaying of ACK segments by

some TCPs, transfer speed varies significantly. During evaluation of the stack, transfer speeds

between 2 and some dozens of KBps were measured. But most of the applications for an

embedded web server do not require transfer speeds of several Mbps.

4.3 API

The wish to enable existing applications as well as to create new embedded applications with

Internet connectivity was an important reason for this project. Without spending excessive time

in understanding the details of TCP/IP, an application developer should be able to use the

functionality of this stack by calling simple functions to query some flags. The API consists of a

set of subroutines for sending and receiving data and a flag register that indicates the current

status of stack.

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Casio EG-800U - Cassiopeia - Win CE 3.0 150 MHz Specifications Page 19