Kantronics KPC-4 - Page 37

Kantronics Host Mode Operation
To operate in the Host Mode with a Kantronics TNC you must first set the INTFACE
command to HOST. After this is set, it will be necessary to perform a soft reset to
enter the Host Mode. This may be accomplished by typing RESET at the cmd: prompt.
If you want the TNC to always operate in the Host Mode, be sure to give the command
PERM. You will also need to set the ABAUD command to the appropriate baud rate
for your terminal. If the ABAUD command is not set, the TNC will run its normal
autobaud routine, looking for an asterisk (*) from the keyboard. When the asterisk is
entered, the TNC will then immediately enter Host Mode. While operating Host Mode,
your program must use hardware flow control (RTS/CTS). Software flow control is not
possible in Host Mode.
Communication Format
Host computer to TNC
Communication from the host to the TNC must occur in blocks. The block of data is
delimited with a FEND character ($C0) at the beginning and end. If the FEND
character appears within the block as valid data, the host must replace this character
with a special sequence, consisting of a FESC ($DB) followed by a TFEND ($DC). One
other special sequence may be required in the event a FESC ($DB) character is
required in the data field. This is accomplished by the special sequence of a FESC
($DB) followed by a TFESC ($DD). These special sequences are the same used in the
KISS code, as implemented by Phil Karn, KA9Q.
After the opening FEND, the next character is the command byte and will indicate
the type of command being given to the TNC. The permissible characters in the
command byte are C, D, or Q. For the KAM only, there are some other combinations
used for non-packet HF mode operation. These will be covered later.
A'C' command byte indicates a command that the TNC will interpret as if it were in
the Command Mode. If the command byte is a 'D', the TNC will consider the data as
data to be transmitted on the specified port and stream. The letter 'Q' in the command
byte will cause the TNC to exit the Host Mode and return to Terminal Mode.
The next byte is the port byte. This byte must be used with every block of type
'D' to signify which port (1 or 2) is to be used for transmission of the data. Type 'C'
blocks must always specify this byte as either a 1 or 2, but this is only used on
those commands that are specific to a port. This would include the CONNECT and
DISCONNECT commands. When using the KAM, the VHF port is selected by a port
byte of '1' and the HF port is '2'. Single port units use port byte '1'.
The fourth byte is the stream byte. This byte determines which stream (A-Z) the TNC
will use for the data. If the stream byte is 0 for a data packet (command byte D), the
data will be sent out UNPROTO. (See the section on the KAM HF modes for more
information.) For commands that do not involve a specific port or stream, the port and
stream bytes are ignored, but must be specified. In these cases, you should address
port 1 stream A.
After these four header bytes, the structure of the block for a command is exactly the
same as if you were entering the command from the Terminal Mode of the TNC. If
entering data to be transmitted, simply place the data in the following bytes. Note that
commands do not need a carriage return included in the data portion of the packet.
After the data or command, terminate the information from the host with a FEND
($C0) character.
HOST 30A
© Copyright 1991, Kantronics, Inc. All Rights Reserved. :
Duplication of this manual or the firmware without April 1, 1991 _ Version 4.0
permission of Kantronics, Inc. is prohibited. Operations Manual