TCC-80, which is powered via the RS-232 ports, provides complete signal conversion be
tween RS-232 and RS-422/485. TCC-80 converts back and forth between RS-232's TxD
and RxD lines and either half duplex 2-wire RS-485 or the balanced signal of full duplex
4-wire RS-422/485. In addition, TCC-80's outputs have comprehensive protection agains
t current overload with built-in 15 KV ESD surge protection. TCC-80 is also designed to p
rovide RS-485 auto data direction control in which the RS-485 driver is enabled automatic
ally when the circuitry senses the TxD output from the RS-232 signal. This means that n
o programming effort is required to control the transmission direction of the RS-485 signal.

RS-232 SerialPort Power
The RS-232 port of TCC-80 is designed
 with a female DB9 socket to connect
 directly to the host PC, with power drawn
 from the TxD, RTS, and DTR lines.
Regardless of whether the signal is high
 or low, TCC-80 is still able to obtain
enough power from the combined force of
 these three data/handshake lines. For
 those applications that do not use the
handshake lines, a DC jack is provided for connecting a 5 to 12 VDC power supply
via a USB power cord or external power
 adaptor.

Optional External Power
Termination is thought to be a critical requirement for port-power devices such as TCC
-80. In most circumstances, termination resistors are used when the RS-422/485 cable
length is longer than 100 m. Regardless of how much the data signal is dissipated, the
termination resistors absorb more than 75 mW of power from the power source when T
CC-80 is unable to use the limited serial power. In other words, if long distance RS-422
/485 transmission or termination is required, and no handshake lines are available, the
n an external USB power cord or DC power supply should be used.

Port Power Dissipation
When installing an RS-232 port-powered TCC-80 converter, it is important to pay attentio
n to the power consumption, RS- 232 cable length, and the RS-422/485 transmission di
stance. In general, TCC-80 itself derives 50 mW from the power source; a standard CO
M port on a host PC can provide 70 to 90 mW of power if the TxD, RTS, and DTR lines
are connected. Moreover, the RS-232 cable length should be shorter than 15 m @ 9600
baudrate to ensure that less power is lost from the host/device to the TCC-80. In the en
d, the rest of the supplied power is used for transmitting the RS-422/485 signal.

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