Epson Multi-mode Data Controller MFJ-1278B - Manual (Page 352)

MFJ-1278B MULTI-MODE APPENDIX E CONVERTING TO TNC-2
CONVERTING THE MFJ-1278B TO "LIKE-TNC 2"
With a simple modification as described in this section, APPENDIX E, the user can easily
convert the MFJ-1278B to a "like TNC 2" controller. Once converted, the MFJ-1278B can
run programs such as NET/ROM™ , THE NET™ and other special firmware that have
been developed for the TNC 2. The modification described below sets the MFJ-1278B into a
"like" TNC 2 mode. What this means is the MFJ-1278B will work like an MFJ-
1270C/1274C TNC-2. The modification forces the MFJ-1278B to operate 1200 baud VHF
packet, and to select Radio Port 1. The modification also forces the terminal baud rate to
4800 baud.
The modification involves replacing IC U27 and U28 with pre-programmed headers as
shown in Figures E-1 and E-2. Firmware EPROM, U23 will be replaced by an EPROM that
contains programs such as NET/ROM™ and THENET™ , etc.
Modification of MFJ-1278B for "Like" TNC 2 operation involved making it to default 4800
baud for the terminal baud rate, 1200 baud radio baud using VHF packet tones on Radio Port
1. The procedure is as follow:
1.
Remove power from the MFJ-1278.
2.
Construct Header U27 by connecting pins 9, 12, 16 and 19 to ground at pin 10.
Connect pins 2, 5 and 15 to +5 Volts at pin 20. See Figure E-1 below.