User's Guide

Table Of Contents

112

File Transfer Utilities

At times it is necessary to upgrade the SkyWay Bridge/Router software. You can do this

remotely using the file transfer utilities, Xmodem, Ymodem, or TFTP. Typically you will

need to upgrade the Runtime Application with a new release of the software.

The three file transfer utilities are Xmodem, Ymodem, and TFTP.

Xmodem

Xmodem is a file transfer protocol with the following ASCII character definitions:

Xmodem is a receiver-driven, asynchronous, 8 data bit protocol. Each packet has the

following format:

where:

When the receiver is ready, it sends a NAK every 10 seconds (up to one minute) until

the transmitter acknowledges the NAK by sending the first packet. The transmitter

continues by sending each packet in turn, always waiting for the packet to be acknowl-

<SOH> 01H This is always the first byte in

each block.

<EOT> 04H This is sent instead of SOH to

mark the end of transmission.

<ACK> 06H Positive Acknowledgement.

<NAK> 15H Negative Acknowledgement

<CAN> 18H Cancel transfer.

<SOH> =01H

<packet> = Packet number, starting at 01, incre-

menting by 1, and wrapping from

0FFH to 00H (not 01H)

<compliment #> = 255 minus the packet number

<data> = 128 bytes of binary data

<checksum> = The sum of the data bytes. Starting

with zero, add each data byte to the

checksum and use only the rightmost

8 bits.