I've had lots of luck with the MAX3100. It's fast and requires just 4 lines:
1) Data in
2) Data out
3) Clock
4) Chip select

It is also capable of open drain interrupt generation upon a number of
different conditions if you need that.

Maxim will sample you one so you can try it for free.

> Does anyone know where I might find an I2C based USART or UART?  I need to
> use three UARTs on a pic17c766 based design and I would rather not add
> another PIC just to get a UART....
>
> +++++++++++++++++++++++++++++++++++++++
> ++      Dan Tye
> ++      Chief Engineer
> ++      Tel-Tron Technologies Corporation
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