8052 uart
I'm not sure what you mean by the term 'Parallel Access'?
I think the two chips already mentioned (FTDI FT2232C and Prolific PL-2313) are the only USB chips with two serial ports I think.
I have never heard of others.
Link for Prolific:
**broken link removed**
The Prolific chip is still in production.
The "littlebrother" PL-2303 is the most used chip in USB<->RS232 converter cables.
Here are original Prolific reference design schematics for PL2303 and PL2313, both as PDFs and OrCAD schematics:
You can buy Prolific chips through:
Maxtek Technology Company
Hsinchu office
Tel: 886-3-5509778
fax: 886-3-5509770
www.maxtek-icrep.com.tw
I can't find anyone who sells the Prolific chips to private persons, but since you have posted in this forum I guess it is for professional use.
FTDI chips are easy to buy as a private person, they are sold in many electronics web-shops.
If you only need one UART you should check the Silicon Laboratories (fomerly Cygnal) CP2101:
https://www.silabs.com/products/microcontroller/interface.asp
This is the most compact and integrated USB to UART converter on the market.
The others requires external resonator and optional EEPROM with vendor ID, device name etc.
CP2101 is the only one with integrated EEPROM and Oscillator, you only need two to three external capacitors and a USB-plug.
But as I said it only has one UART port.