I. Summary
With rapid development of computer industry, USB is taking the place of various
kinds of traditional low speed peripheral interfaces. However, RS-485/RS-422
interface designs are still used in many of the important facilities under current
industrial environment; therefore, converter is used by many users to implement the
data transmission from USB of a computer to RS-485/RS-422 equipments.
UT-890A is a universal USB/RS-485/422 converter that without external power
supply needed. Compatible with USB, RS-422 and RS-485 standards, UT-890A is
capable to perform the conversion from single-ended USB signal into balance
differenced signal of RS-422 or RS-485. Quick state-of-the-art transient voltage
suppressor (TVS) and discharge tube are adopted to protect the RS-422/RS-485
interfaces. Under normal conditions, the TVS tube is in the state of high resistance.
However, when both ends of the TVS tube are hit by a transient high energy, the
impedance at both ends can be depressed by the TVS at a very high speed, and after
absorbing a high current, the voltage between the two ends is suppressed and kept at
a pre-set value, therefore no damage is caused to the electrical components behind by
the transient high voltage impact. The protector can effectively restrain lightning or
ESD (electro static discharge) with a protection voltage of 600W on each line for
lightning surge and surge voltage or transient over voltage possibly caused up by
various reasons, and at the same time, a high-speed transmission of RS-422/ RS-485
interfaces is ensured by the tiny capacitance between the poles. RJ-45 and DB9 male
connectors are used for connection from RS-422 and RS-485 to other equipments.
The unique I/O circuit of the internal zero delay auto transceiver contained in the
converter controls the data stream direction automatically without any handshaking
signal (for example RTS, DTR etc). The converter is plug-and-play without any
jumper settings needed for mode shift between full duplex (RS-422) and half duplex
(RS-485). All these features ensure a universal application on all the existing
communication software and hardware interfaces.
A reliable and stable point-to-point and point-to-multipoint communication
can be ensured by UT-890A interface converter. For point-to-multipoint
communication, as many as 32 interface facilities of RS-422 or RS-485 standard can
