Features and Benefits

• External power source supported but not required
• Compact size
• Converts RS-422, and both 2-wire and 4-wire RS-485
• RS-485 automatic data direction control
• Automatic baudrate detection
• 15 KV serial ESD protection
• Built-in 120-ohm termination resistors
• 2.5 KV isolation (for TCC-80I only)
• LED port power indicator

Introduction

The TCC-80/80I provides complete signal conversion between RS-232 and RS-422/485, without requiring an external power source. It supports both half duplex 2-wire RS-485 and full duplex 4-wire RS-422/485, either of which can be converted between RS-232's TxD and RxD lines. In addition,the TCC-80/80I's 15 KV ESD protection guards against damage from electrostatic discharge. The TCC-80I is the world's first high-speed, port-powered converter with 2.5 KV isolation.

Automatic data direction control is also provided for RS-485, in which the RS-485 driver is enabled automatically when the circuitry senses the TxD output from the RS-232 signal. This means that no programming effort is required to control the transmission direction of the RS-485 signal. Moreover, the TCC-80I patented LED port power indicator can let you check if TCC-80I is receiving enough power or not.

Port Power over RS-232

The RS-232 port of the TCC-80 is a DB9 female socket that can connect directly to the host PC, with power drawn from the TxD, RTS, or DTR line. Regardless of whether the signal is high or low, the TCC-80 can obtain enough power from the data/handshake line. However, external power can be used if the handshake line is not available, if the serial cable is too long, or if the RS-232 device is a low power device. For external power, a 5 to 12 VDC power supply can be connected using an adaptor or a USB power cord.

Optional External Power

Termination is a critical requirement for port-powered devices such as the TCC-80. In most circumstances, termination resistors are used if the RS-422/485 cable is longer than 100 m. Regardless of how much the data signal is dissipated, the termination resistors absorb more than 75 mW of power. In other words, if long distance RS-422/485 transmission or termination is required, then an external USB power cord or DC power supply should be used.

Port Power Dissipation

When installing a TCC-80 converter, it is important to pay attention to power consumption, RS-232 cable length, and RS-422/485 transmission distance. In general, the TCC-80 obtains 50 mW from the power source. Standard PC COM ports can provide 70 to 90 mW of power if the TxD, RTS, and DTR lines are connected. Moreover, the RS-232 cable should be shorter than 15 m (@ 9600 bps) to ensure that less power is lost from the host/device to the TCC-80. The remainder of the supplied power is used for transmitting the RS-422/485 signal.

Port Power and Optical Isolation

The RS-232 port of the TCC-80 is a DB9 female socket that can connect directly to the host PC, with power drawn from the TxD line. Electrical 2.5 KV isolation is achieved with a photo coupler that transforms the electrical signal into light, and then re-transforms the light back into an electrical signal on the other side. In this way, the two electrical circuits are completely isolated from each other. This also protects the devices from ground loop currents, reduces damage caused by data loss, and prevents damage to the communication interfaces.

LED Port Power Indicator

It's easy enough to test the serial device with a multimeter to determine that the serial device will provide enough power to the media converter. However, it's even easier to let the TCC-80I test the device for you. Simply connect the TCC-80I to the device's RS-232 port and set the SW4 switch to Test mode. If the patented port power LED indicator lights up, the TCC-80I is receiving enough power. If the LED does not light up, you will need to attach an external power source to the TCC-80I.