# US 2014/0192905 A1 · Apparatus for converting terminal polarity for r s communication

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- Number: US 2014/0192905 A1
- Document ID: US20140192905A1
- Status: Published application
- Kind: A1
- Application number: 14/092,109
- Filed: 2013-11-27
- Published: 2014-07-10
- Earliest claimed: 2013-01-04
- Assignees: Lsis Co., Ltd.
- Applicants: Lsis Co., Ltd.
- Inventors: Hyung Lae KIM
- Web page: https://patentgrep.com/patent/US20140192905A1

## CPC

- H04B 3/02: Details
- H04B: TRANSMISSION

## Abstract

An apparatus for converting terminal polarity for RS communication includes a comparator configured to discriminate polarities of a first signal line and a second signal line by comparing voltage levels indicated on the first and second signal lines of a cable for RS-485 communication, a switch unit configured to connect a TRXD+ terminal to the first signal line and connect a TRXD− terminal to the second signal line, or to connect a TRXD+ terminal to the second signal line or connect a TRXD− terminal to the first signal line in response to a provided switch control signal, and a switch controller configured to transmit the switch control signal to the switch unit in response to a polarity discrimination result by the comparator relative to the first signal line and the second signal line.

## Claims

### Claim 1

An apparatus for converting terminal polarity for RS communication, the apparatus comprising:
a comparator configured to discriminate polarities of a first signal line and a second signal line by comparing voltage levels indicated on the first and second signal lines of a cable for RS-485 communication;
a switch unit configured to connect a TRXD+ terminal to the first signal line and connect a TRXD− terminal to the second signal line, or to connect a TRXD+ terminal to the second signal line or connect a TRXD− terminal to the first signal line in response to a provided switch control signal; and
a switch controller configured to transmit the switch control signal to the switch unit in response to a polarity discrimination result by the comparator relative to the first signal line and the second signal line.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the comparator discriminates the polarity of the first signal line and the polarity of the second signal line using output voltages relative to the first signal line and the second signal line applied to an input terminal of mutually different polarities.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the comparator includes a first comparator configured to receive a voltage of the first signal line and a voltage of the second signal line through a minus input terminal and a plus input terminal respectively to discriminate the polarity of the first signal line and the polarity of the second signal line and to output a signal as a result of the discrimination, and a second comparator configured to receive a voltage of the first signal line and a voltage of the second signal line through a plus input terminal and a minus input terminal respectively to discriminate the polarity of the first signal line and the polarity of the second signal line and to output a signal as a result of the discrimination.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein the switch unit includes a first D flip flop, a second D flip flop, a first AND element, a second AND element and an OR element, wherein
two input terminals of the first AND element are respectively connected to an output terminal of the first comparator and to a Q′ terminal of the second D flip flop,
two input terminals of the second AND element are respectively connected to an output terminal of the second comparator and to a Q′ terminal of the first D flip flop,
a reset signal from a host is inputted to a RESET terminal of the first D flip flop, and a SET terminal is connected to an output terminal of the first AND element,
a reset signal from the host is inputted to a RESET terminal of the second D flip flop, and a SET terminal is connected to an output terminal of the OR element,
an output signal of the second AND element and a Q terminal signal-inversed signal of the first D flip flop are inputted to two input terminal of the OR element, and
the switch control signal is generated by using a Q terminal signal of the first D flip flop and a Q terminal signal of the second D flip flop.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the switch unit includes a first switch configured to connect the TRXD+ terminal to the first signal line or disconnect the TRXD+ terminal from the first signal line, a second switch unit configured to connect the TRXD+ terminal to the second signal line or disconnect the TRXD+ terminal from the second signal line, a third switch configured to connect the TRXD− terminal to the second signal line or disconnect the TRXD− terminal from the second signal line, and a fourth switch unit configured to connect the TRXD− terminal to the first signal line or disconnect the TRXD− terminal from the first signal line.

### Claim 6 (depends on 5)

The apparatus of claim 5, wherein the first, second, third and fourth switch units are turned on when an inputted switch control signal is high, and the first, second, third and fourth switch units are turned off when an inputted switch control signal is low.

### Claim 7 (depends on 5)

The apparatus of claim 5, wherein the switch controller reverses the Q terminal signal of the first D flip flop for transmission as control signals of the first switch and the third switch, and reverses the Q terminal signal of the second D flip flop for transmission as control signals of the second switch and the fourth switch.