WEFAX
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Some considerations for the RS-232 port. When the TNC is set in WEFAX Mode, it will send pixel
by pixel bytes to your computer continually until you send it a
Ctrl-C
or turn it off! When in WEFAX
Mode, the TNC will do nothing else; it is simply too busy handling all that data. The bytes sent to
your computer on the RS-232 receive data line include one start bit, eight pixel bits and one stop
bit. The most significant bit is the left-hand bit for your display. In effect then, if you specify
WEFAX 1280, the TNC will send you bytes every 8/1280 of a second or 160 bytes per second.
Now for printing. We recommend that you use a printer that is Epson graphics compatible with the
PC or Commodore. If you write the program and your printer can handle 600+ pixel per line (this
is about 60 dots per inch or dpi) and at least 32 lines per inch vertically, then it should be capable
of printing WEFAX maps and charts. Note, that six lines per inch of standard text is roughly equiva-
lent to 72 lines per inch of graphics.
What about the structure of your program? We recommend that you include a simple terminal pro-
gram that would be used to set the basic parameters of your TNC (ABAUD, MAXUSERS etc.). In
addition, we recommend that you have a software loop that is interruptible by the arrival of pixel
bytes. These bytes would then be stored and/or displayed in the interrupt routine. Once the bytes
are processed, the interrupt routine would return to the main loop to await more pixel bytes from
the TNC. If you use BASIC, BASICA or compiled BASIC, then ON COM statement is useful. Look in
the manual under trapping.
