HOST
29
KAM
HF Modes
When operating non-packet modes (i.e. RTTY, ASCII, AMTOR or CW) with the
KAM
, a few additio-
nal host to TNC frames are required. First, select the mode with standard command structures as
described above (e.g. FEND C2ARTTY 75 FEND). Data that you wish to transmit to the other sta-
tion should have command by 'D', port byte '2' and stream by '0'. Special host frames for these
modes are:
FEND T FEND
Enter transmit mode
FEND E FEND
Enter receive mode when buffer empty
FEND R FEND
Enter receive mode immediately
FEND X FEND
Return HF port to Packet mode
FEND Ctrl-X FEND
Clear the transmit buffer in KAM HF
TNC to Host Computer
Communication from the TNC to the host also occurs in blocks which are delimited at beginning
and end with FEND characters ($C0).
After the beginning FEND, the next character is the status byte. A status byte 'C' is a response to a
command from the host with the command byte 'C'. A status byte of 'D' indicates, that the data
was received on a connected stream (see the section below on the
KAM
HF operation). 'M' in the
status byte means that the data in this block is the result of the monitor commands.
A status byte of 'S' is a status message caused by a change in the link state. Such messages in-
clude the *** CONNECTED TO, *** DISCONNECTED and FMR sent. A special 'S' block of data con-
sists of two FEND characters, the characters S00 and another FEND character. This indicates that
the TNC has performed a soft reset and all existing connections (if any) are not longer valid. This
is equivalent to the TNC having just been turned on. A data block with the status byte 'R' is a
*** CONNECT REQUEST. A block with status byte 'T' is the result of the TRACE command. Port
and stream bytes (defined below) are valid for 'D' and 'S'blocks, but only the port byte is valid for
'T', 'M' and 'R' blocks.
The port byte follows the status byte and will contain the port number the specific information is
from. This will be a '1' if the TNC is in single port operation or a '1' or '2' if in dual port operation.
When using the
KAM
, the VHF port is indicated by a port byte of '1' and the HF port is '2'. Single
port units use port byte '1'.
The stream byte follows the port byte. The stream byte will be 'A' – 'Z' for data on the connected
streams. Data being sent to the host which is not connected data will have the stream by set to
'0'.
If the TNC returns a 'C' status block with no data, this indicates that the command was accepted.
This will occur on connect and disconnect commands.
A 'T' block from the host (TRACE information) is raw data and not a hex dump of the received
packet.
The KISS transparency (FESC, FEND, TFEND and TFESC) described above is always applied to all
blocks.
