RS-422 support

Does the Plugable USB to RS-232 DB9 Serial Adapter (Prolific PL2303HX Chipset) support RS422?

Hi RJ,

Thanks for posting your question here, I’ll be happy to assist. The product information page for the PL2303 chip that’s in our USB to Serial cable does list RS-422 support.

Here’s the link:…

I haven’t tested it myself though, so I am unfamiliar with it’s implementation but we’ll do our best to help if you have any troubles.

Thanks for asking,

Plugable Technologies

I noticed in the data sheet that several pins need to be driven externally to 5V. My main question is… are those pins driven high internally from the USB or do I need to do that on DB9 side?

Hi RJ,

According to the product overview available here:…

The PL2303 provides flexible signal level requirement on the RS-232 serial port side also allows the PL-2303HX to connect directly to 3.3V ~ 1.8V devices.

Hope this helps.


Plugable Technologies

Late reply on this, as I came across this thread while searching for information on using this adapter to connect to a device with 3.3v signal levels.

While the PL-2303HX chip used in this adapter WILL work with 3.3v signals, there is also a SP213EEA chip (manufactured by Sipex) that converts the TTL voltage levels from the 2303 to 12v levels, -12v-12v was the listed range on this chip, but without further checking of the circuit I can’t verify that it uses this full range.

Short story, attempting to use this serial adapter with a 3.3v level connection will not work, it will only receive/transmit garbage data at best.