CONNECT COMPUTER
5
Since there are so many computers on the market, it is impossible to provide interfacing informa-
tion on all of them. The following chart shows what pins are used in the TNC by name and number
and the corresponding pin to connect to for the most commonly used computer connectors. A
general rule, if you have a computer not covered here that has a serial data port, wire pins of the
same name together. Limited information on some of the other common computers will follow.
Transmit Data (TXD), Receive Data (RXD) and Signal Ground (SG) must always be
wired in order for the TNC and the computer to exchange any data. Many terminal pro-
grams also require the use of hardware flow control from the TNC. For hardware flow
control Request To Send (RTS) and Clear To Send (CTS) must also be wired. Check the
documentation toyour terminal program to see if any other wires are required. DO NOT
CONNECT ALL 25 (9) WIRES.
Some programs want to see Data Set Ready (DSR) to know that the TNC is there before operating.
If this is the case, wire both DSR and Data Terminal Ready (DTR). Or sometimes you can satisfy
the program's need by jumpering these two pins at the computer end of the cable. Data Carrier
Detect (DCD) is needed by some BBS software to know that a connection has taken place. This
would require wiring DCD. Some phone modem programs also want to see a connection before al-
lowing you to even talk to the TNC. This case can usually be solved by jumpering DCD to DTR at
the computer end of the cable. If your computer requires DSR and also DCD, it is perfectly accept-
able to jumper all three pins (DTR, DSR and DCD) together on the computer end of the cable.
Note: DCD, DSR and DTR connections are not pre-wired in the provided cable.
The TNC is wired as DCE (Data Communication Equipment). DCE equipment always send its data
on the RXD wire. DTE (Data Terminal Equipment) talks on TXD. This means that, if a computer is
wired internally as DCE and attached to the TNC, it will need to have TXD from the computer
wired to RXD on the TNC and RXD from the computer wired to TXD of the TNC. Otherwise they
will both be talking on the same wire and never hear what is said. If properly implemented by the
DCE computer, hardware flow control may be used by connecting RTS from each device to CTS on
the other device.
Caution: Make sure the power to the transceivers, computer and TNC is OFF before connecting
any cables.
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