TINY-2/MICRO-2 Technical Ref., 2. Ed 1989
- 14 -
The signals used at connector J5 are at standard TTL interface levels. A TTL high is greater than
+2.4 Volts but less than +5.25 Volts. A TTL low is less than 0.4 Volts but greater than 0 Volts.
DO NOT connect an RS-232C level modem directly to J5!
If you elect to use an off-board modem, be sure to properly shield the interconnecting cables for
RFI protection.
J5 Pin Definitions
The following information is primarily for those who wish to interface external modems to the
packet controller. Familiarity with modem and serial data channel terms is assumed.
Pin 1 Carrier Detect Input
This pin tells the SIO radio port that a valid data carrier has been detected. It should be
pulled high when no carrier is detected and low when a carrier is present. It is normally
jumpered to pin 2 when the on-board modem is used.
Pin 2 Carrier Detect Output
This pin is an output from the on-board modem (via an inverter gate) and provides the
necessary signals required by pin 1 above. It is normally jumpered to pin 1 when the on-
board modem is used.
Pin 3 SIO Special Interrupt Input
This pin is routed to the radio port DCD input pin on the SIO. This pin is normally jumpered
to pin 4 when the on-board modem is used.
Pin 4 SIO Special Interrupt Generator Output
This signal is an output from the on-board modem. It is normally jumpered to pin 3 when
the on-board modem is used.
Pin 5 SIO RTS Output
This signal is used for transmitter activation. It activates the PTT pin of the radio connector
via the watch-dog timer. The SIO will pull this output low when the TINY-2/MICRO-2 wants
to transmit; otherwise it will remain high. This pin is normally jumpered to pin 6 when the
on-board modem is used.
Pin 6 Modem RTS Input
This Signal is an input to the on-board modem. It should be left high and pulled low only
when transmission is desired. This pin is normally jumpered to pin 5 when the on-board
modem is used,
Pin 7 CONNECT Status Output
This pin is an output from the SIO. It is normally low and goes high only when the TINY-
2/MICRO-2 is in a connected state. Its Status is reflected by the CON LED.
Pin 8 Unacknowledged Packets Pending Status Output
This pin is an output from the SIO. It is normally low and goes high only when the TINY-
2/MICRO-2 has unacknowledged packets in its transmit buffer. Its Status is reflected by the
STA LED.