If I have two boards connected via RS422, do the same transceiver ICs have to be used at either side, or is it sufficient to have logic level voltages be the same even using different model ICs?
\$\begingroup\$
\$\endgroup\$
1
-
2\$\begingroup\$ The two boards don't have to use the same chip, as long as they respect the standard (and standards exist for interoperability)! Should not be required, but you can check both datasheets to see if some problem arises... \$\endgroup\$– linuxfan says Reinstate MonicaCommented Oct 13, 2022 at 9:49
Add a comment
|
4 Answers
\$\begingroup\$
\$\endgroup\$
Neither the transceivers nor the logic levels need to be identical.
The RS-422 standard requires that transmitters must be able to generate a differential output voltage of at least ±2 V over a 100 Ω load. (And that receivers must be able to handle at least ±200 mV.) All 3.3 V and 5 V transceivers can handle this.
\$\begingroup\$
\$\endgroup\$
Different brands of transceivers should be largely compatible else, how could someone ever hope to design an interface circuit. This is why we have communication interface standards.
\$\begingroup\$
\$\endgroup\$
2
RS-422 is a standard. If the circuits at both ends of the wire comply with the standard, then they will be able to talk to each other. If either one of them doesn't comply, then it isn't really an RS-422 link.
-
\$\begingroup\$ Strictly speaking, TIA/EIA-422 is a standard and "RS-422" is the name of some early draft from the 1970s. \$\endgroup\$– LundinCommented Oct 14, 2022 at 12:53
-
1\$\begingroup\$ @Lundin, I would say, "TIA/EIA-422" is the official title of the standard, and "RS-422" now is a common name for the same thing. "RS-422," originally was the title of a formal recommendation ("RS"=>"Recommended Standard") that ultimately led to the creation and acceptance of the TIA/EIA standard. \$\endgroup\$ Commented Oct 14, 2022 at 13:14
\$\begingroup\$
\$\endgroup\$
They can interface with each other, since RS-422 is the standard.
That said, different transceivers can have varying levels of speed, noise immunity, fault tolerance, drive capability (number of devices) etc. So although all transceivers will meet a baseline compatibility, they are not necessarily interchangeable or functional in all setups.
