TINY-2/MICRO-2 Technical Ref., 2. Ed 1989
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COMPUTER INTERFACING
The TINY-2/MICRO-2 packet controller communicates with the computer or terminal through a se-
rial port using either RS-232C or "TTL" level signals. One of these signal levels should properly in-
terface to most computers. See the Appendices to this manual for specific computer interfacing in-
structions.
RS-232 Port Signals
The serial port connectors on the TINY-2/MICRO-2 packet controller are on the rear panel marked
"RS-232" and "TTL Computer". The pins on the serial port connector of packet controller that must
be connected are shown in the following table. This is commonly called a "three-wire" RS-232 ca-
ble.
RS-232 Serial Port "3 Wire" Cable Wiring for DB-25
Computer DB-25 TINY-2/MICRO-2
1 and 7 –––––––– 5
2 ––––––––––––– 3
3 ––––––––––––– 2
RS-232 Serial Port "3 Wire" Cable Wiring for DE-9
Computer DE-9 TINY-2/MICRO-2
5 and Shell ––––– 5
2 ––––––––––––– 2
3 ––––––––––––– 3
The packet controller is configured as Data Communications Equipment (DCE), the technical term
for an RS-232C modem. Most computers and terminals are configured as Data Terminal Equipment
(DTE). Specifically, the packet controller connector is an IBM "AT style" using a male DE-9 connec-
tor, wired as DCE rather than DTE. If you use an "AT" PC or portable Computer with a 9-pin serial
port, you can wire cable connector pins 2 through 8 directly (pin 2 to pin 2, etc.).
Pin 1 on the TINY-2/MICRO-2 is the Data Carrier Detect (DCD) signal which goes high (true) when
the packet controller is in the "connected" state. This is analogous to the DCD signal on telephone
modems, i.e. the pin is asserted when a communication connection exists. Pin 9 is used as an aux-
iliary radio carrier detect input. This pin may also be used when two or more packet controllers are
mated for use with network firmware such as the NET/ROM or ROSE EPROM. More detailed infor-
mation is presented later in the manual.
Some computers require that Clear To Send (CTS) of the computer serial port connector (pin 5 of a
DB-25 or pin 8 of a DE-9) be connected to an appropriate signal. Others may require connections
for Data Carrier Detect (DCD) (pin 8/pin 1) and Data Terminal Ready (DTR) (pin 20/pin 4). You
may jumper the computer's input and output signals on DB-25 pins 4/5 (DE-9 pins 7/8), and on
DB-25 pins 6/8/20 (DE-9 pins 6/1/4) in addition to the connections shown in the "3 wire" RS-232
diagram above, or build an "8 wire" interface cable as shown below:
Jumpering RTS/CTS and DTR/DSR/DCD at the Computer Gable End
DB-25:
DE-9:
4 –––––– 5
7 –––––– 8
6 –––––– 8 –––––– 20
1 –––––– 4 –––––– 6
