Kantronics MT1200, User Manual

Page: 63 / 157

and turn the unit off and then back on. Be aware that there is no data flow control.
Exiting LSUB Mode
If you want to exit LSUB mode to "fine tune" parameter settings (or for any other
reason), the Command mode of the modem can be regained by using the transparent
data escape sequence, i.e., by sending a series of three control-Cs (unless a different
control character has been defined). (See TRANS command in the Reference Manual).
TUP mode (Transparent Unproto Packet)
TUP Mode Description
The TUP mode protocol utilizes the Unproto mode of the AX.25 protocol, allowing
digipeaters (VIA path specified with UNPROTO command) to be used in order to
effectively extend the range of a radio data system beyond simplex distance. This
protocol uses the standard AX.25 CRC-16 error-checking to provide a high degree of
data integrity. Data is sent and received in a totally transparent fashion, allowing all
ASCII characters to be utilized (hex 00 through hex FF).
I.
Radio transmission is based on
the PACTIME AFTER parameter setting of the modem, the setting of the carrier detect
method, and the settings of the slot and persist channel access algorithm. Any data that
is received by the modem via the radio is output to the serial port
only if it contains no
detectable errors. The received data will be exactly the same as the data that was sent
to the input serial port of the transmitting mode, without any address headers or added
formatting of the data. The modem is capable of selectively filtering monitored data from
or to different modem addresses using the BUDLIST command.
If digipeaters must be used to extend the range of the system, the information frame
sent by any modems in the system will be output to the serial ports of the receiving
modems only once, regardless of how many times it was received correctly. Also, data
sent by any modem will not be decoded by itself when the data is digipeated. The TUP
mode protocol provides an automatic "Time to Live" timer that inhibits any modem from
transmitting or receiving additional data until sufficient time has expired to allow in-
progress data to travel through all the digipeaters specified in the UNPROTO field of the
originating modem. Since the time for a given packet to travel the entire UNPROTO
path may vary due to the presence of other signals or noise, TUPTIME is used to
impose an additional delay time, if needed, during which each modem will be inhibited
from decoding or transmitting new data. This setting can be determined experimentally.
It is important to note that TUPTIME applies
only to the receiving modems and should
55