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AR-210 Manual
3-8
Many terminal programs and file transfer programs for home computers do not implant flow con-
trol in software and may so-called RS-232C ports do not support hardware flow control.
Even if the RTS and CTS lines appear at the connector, software that directly reads the CTS line
may be required in order for flow control to be implemented. If you find that the TNCs seem to
lose data during file transfers, immediately suspect a flow control problem.
XON/XOFF FLOW CONTROL
If you are using a terminal rather than that a computer, or if your computer does not support
RTS/CTS flow control, you can use XON/XOFF flow control. You can establish this method by set-
ting
XFLOW ON
. The special flow control characters are set to CTRL-S and CTRL-Q by default.
In the Command Mode, the TNC input buffer may fill up if you try to type too long a command. In
the data mode, the buffer may fill up if you are using your computer to transfer data at a rate that
that is faster than the data rate for radio transmission, if radio data transmission has slowed down
due to noise or other users on the channel, or if the operator or computer at the other end has
stopped the output from his TNC.
The TNC will send the terminal an XOFF character when there is room remaining for about ten
characters in the buffer. If you continue sending data until there are only five spaces left, the TNC
will send and XOFF character after each character received. When the buffer fills up completely,
data will be lost. When the buffer empties out, the TNC will send a single XON character to the ter-
minal.
If you disable
XON
and
XOFF
by setting them to
0
, the TNC will automatically use the RTS/CTS
flow control to stop input from the terminal.
XON/XOFF flow control is normally disabled in the Transparent Mode. This is done because charac-
ters are treated as data; therefore, the XON and XOFF characters will not be recognized.
If you can not use RTS/CTS flow control, you may enable the XON and XOFF characters (the com-
mands from the TNC to the terminal) by setting
TXFLOW ON
and
XFLOW ON
. START and STOP
characters (the command to the TNC from the terminal), however, will still be treated as data.
HARDWARE FLOW CONTROL
This method of flow control is preferred, since it usually does not depend on the programming of a
particular communications program.
The AR-210 conforms to the TAPR TNC-2 standard which users DTR (Data Terminal Ready) instead
of RTS (Request To Send).
If you wish to uses DCD (Data Carrier Detect) signal to control your software or your software re-
quires DCD ON/OFF, remove JP-1. If you remove the JP-1, the TNC will provides +8 VDC for con-
nected state and –8 VDC for none-connected state, Refer to the figure 2-1 for the location of JP-1.
DISPLAY OPTIONS
Several parameters control the way output is formatted for display on your terminal. Most of these
are parameters that are determined by the display capabilities of your terminal and changes only if
you change terminals.
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