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ZUBAIR136
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Join Date: Oct 2018
Posts: 5

Difference Between RS232, RS485, RS422

10/04/2018 12:59 AM

i am new in plc programming . i know the basics difference between the rs232, rs422, rs485. but i am little bit confused in it. so i have the following question regarding these terms.
1. can these protocols communicate with each other i mean rs232 can communicate with rs422 or rs485 and same.
2. my plc has port rs422 but i can connect it with my laptop serial port which is rs232 ?
3. what are the main important points that kept in mind during communication or cross communications.
any help will be greatly appreciated.
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Pathfinder Tags: RS232 RS422 RS485
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Anonymous Poster #1
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Re: Difference between RS232, RS485 , RS422

10/04/2018 2:54 AM

Read this.
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PWSlack
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#2

Re: Difference between RS232, RS485 , RS422

10/04/2018 3:04 AM

A1) yes, with suitable interfaces.

A2) yes, with a suitable interface.

A3) See #1⇑ and the links therein.

Also, review the PLC manufacturer's literature on methods of connecting the two. If in doubt, pick up the phone to its Technical Helpline, because on the other end are people who have seen it, done it and have secondhand T-shirts on internet auction sites.

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redfred
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#3

Re: Difference Between RS232, RS485, RS422

10/04/2018 9:44 AM

All three of those are hardware standards. In other words; the number of wires, the impedance of the wires, the voltage levels, noise immunity, nodal configuration and a host of other physical attributes are codified by each of these three standards. As such an interface circuit board between these circuits can usually be placed to allow transparent communication between them but just connecting the two circuits together with just wire will usually lead to no communication.

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DavidSMullins
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Re: Difference Between RS232, RS485, RS422

10/05/2018 11:36 AM

As Red sed, RSxxx are hardware standards or electrical signalling standards. Also note, there are several data protocols that can communicate on any of the RS electrical signalling schemes such as Modbus or DeviceNet. This is like the language your PLC speaks over the RSxxx wires.
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lyn
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Re: Difference Between RS232, RS485, RS422

10/04/2018 10:59 AM

Difference between RS232,RS422,RS485-RS232 ... - RF Wireless World
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rwilliams
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Re: Difference Between RS232, RS485, RS422

10/05/2018 5:07 PM

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Relativity PL
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#5

Re: Difference Between RS232, RS485, RS422

10/04/2018 10:23 PM

Here's an example of an available RS232 > RS422/RS485 hardware interface:

https://www.weartronics.com/products.php?sku=TRP-C06
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MikeMack747
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#6

Re: Difference Between RS232, RS485, RS422

10/05/2018 8:54 AM

You will need converters to change RS232 to 422 and 485.

RS232 was created to transmit data over telephone lines, and has all the handshaking capabilities to do so. RS 422 and 485 have lower voltages and can support faster baud rates for modern equipment.

All these communications protocols are available have USB converters available, and I use them all to test a plethora of different products.

You will need to know the COM port number, baud rate, number of data bits, parity (and if the parity changes for send and receive) Termination character (and if it is enabled), flow control, and number of stop bits. This data will be in the datasheet/manual for the PLC you are using

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