Terminal node controller
A Terminal Node Controller (TNC) is a modem for packet radio operation in amateur radio . It establishes the connection between the computer and the radio and is connected to the serial or parallel interface and the microphone and loudspeaker connection of the radio. In addition, an operating voltage is required, usually DC voltage supplied via a plug, in exceptional cases, as with the TNC1, the mains AC voltage directly.
Development at TAPR
The TAPR (Tucson Amateur Packet Radio Corp.) developed in 1983 (TNC = Terminal Node Controller), which data in which a computer card 'TNC1' AX.25 send protocol and could receive. With the further development, the TNC2 in 1985 , the rapid development of the packet radio mode began in Germany. The principle of packet radio was also used in later developed modes, e.g. B. APRS .
The part of the TNC that compiles the data packets or breaks them down again, taking the correct checksum into account , is also called PAD ( Packet Assembler and Disassembler ). The PAD in the TNC is a small, independent computer. This consists of a microprocessor, a ROM in which the firmware (TF / TAPR etc.) is stored, a battery-backed RAM in which the parameter settings, the received and the data to be sent are saved, and an interface module that connects to the Terminal and modem done, additional logic modules and usually a modem. The PAD converts the serial ( RS232 or USB ) signals supplied by the computer (mostly the AX.25 protocol is used) into a digital code (mostly NRZI ). So that the digital code (consisting of logical zeros and ones) can also be sent via the analog radio device, it is modulated with the help of the modem.
Further developments
Various further developments of the TNC2 followed, which made it possible to connect just one radio device directly to a computer.
In 1993 the TNC3S was developed in Germany, with which it was now possible to have two radios controlled by one computer. The computing power of the TNC3S was even sufficient for setting up a packet radio network node ( digipeater ), so that the computer could be replaced as the central unit of the digipeater. The TNC31 is the small version of the TNC3 with only one modem slot.
As the next step, the TNC4E was developed in Germany in 1997, which now provided for the connection of three radio devices and had an integrated Ethernet connection for communication with computers and other TNC4Es. The chips used to build the TNC4E are Motorola MC68EN302PV20 and the MC68160FB. The modems from Symek and DK9SJ enable baud rates of up to 614 kbit / s. The software for the TNC4 is XNet and is being further developed by DL1GJI on the basis of TCP / IP (see also Internet protocol family ).
The last known further development is the DLC7. The DLC7 is a dual port controller (often also called a dual link controller or data link controller) and the most powerful Ethernet TNC on the market. With its two HDLC ports of 10 Mbit / s each, fast link routes or user access can be implemented. A 32-bit ARM7 RISC processor with approx. 50 MHz clock frequency is installed as the core . The internal SDRAM work memory comprises 32 MB. As an external memory, e.g. A CF card can be inserted, for example for software, configuration files or mailbox data. Usually 512 MB to 1 GB are used, but up to 4 GB can also be used. The interfaces are two internal HDLC slots for a dual port modem DM307 (4800 baud - 307200 baud), up to two COM interfaces for additional modems and a 10/100 Mbit / s Ethernet interface for connection to a network or other DLC-Link controllers. These link controllers are slimmed-down DLC7s with 16 MB SDRAM and without a CF card slot, but offer two additional HDLC slots for the DM307 dual-port modem. This means that powerful and energy-saving digipeaters can be set up with fast link connections. XNET from Version 1.39 Beta is suitable as control software.
Modulation method
Modems for the modulation types AFSK , FSK and GMSK are built into the TNC2 or available as plug-in cards for the TNC3 and TNC4. All common transmission methods use simple FM-modulated transmitters that are connected to the Terminal Node Controller or its modem. Some modems are suitable for linear modulation types ( QPSK ), but in contrast to FM modulation, these signals do not have a constant envelope and require linear signal amplifiers in the transmitter and corresponding receiver (without limiter).
| Technical specifications | TNC2 / TNC21 | TNC3 | TNC31 | TNC4e | DLC7 |
|---|---|---|---|---|---|
| Processor core: | Z80 CPU + Z80 SIO, 5 MHz | MC68302, 16bit, 14 MHz | MC68302, 8bit, 14 MHz | MC68EN302, 16bit, 20 MHz | 32bit RISC ARM7 50 MHz |
| RAM / ROM: | 32k EPROM + 32k SRAM | 256k-1 Mbyte Flash
+ 256k-2MB SRAM |
128-512 kbyte flash
+ 128-512kB SRAM |
1 Mbyte Flash
+ 1-4MB SRAM |
4 Mbyte 16bit Flash |
| Interfaces: | Data flash interface | ||||
| 1 × HDLC (19kbit / s) | 2 × HDLC (1.2Mbit / s) | 1 × HDLC (1.2Mbit / s) | 3 × HDLC (1.2Mbit / s) | 2 × HDLC (10Mbit / s) | |
| 1 × RS232 | 1 × RS232 | 1 × RS232 | 1 × RS232, 1 × DCF77 | 2 × RS232 | |
| 10Mbit / s Ethernet | 10 / 100Mbit / s Ethernet | ||||
| Bus system: | I2C bus | ||||
| Card format: | mostly 100 × 160mm | 120 × 170mm | 120 × 100mm | 120 × 180mm | Euro card 100 × 160mm |
Interfaces
In the meantime (2012) 6-pin mini-DIN connections have established themselves as a quasi-standard for the connection between transceiver and TNC . For example, the Icom IC-910H has the following assignment:
| Pin code | designation | Occupancy |
|---|---|---|
| 1 | DATA IN (MOD) | Data signal input (1200 and 9600 bit / s) |
| 2 | GND | Dimensions |
| 3 | PTT | Push to talk - send switch |
| 4th | DATA OUT (DEMOD) | Data signal output 9600 bit / s |
| 5 | AF OUT (SPKR) | NF (low frequency) output (1200 bit / s) |
The signal directions are named from the point of view of the radio.
RS232 is used for communication between the TNC and the PC, partly also encapsulated in USB via the CDC class as a virtual serial interface.
Web links
Individual evidence
- ↑ IC-910H Instruction Manual Icom inc. America 2002. Retrieved July 18, 2012