USART functions with Arduino (newbie question)

Can anyone answer the question below? Sorry if I do an injustice to any of the facts, I'm a newbie.

Is there a Usart library somewhere? I have looked at the serial library (maybe I missed something), but I dont see anything that allows me to switch between asynchronous communication (uart) and synchronous communication (s in usart). Assuming you can, what would you use as the clock? Is there some pin on the 328 somewhere that gives the system clock? maybe you set an output pin as the clock??

Basically what I want to do is communicate with a chip that requires it's configuration information to be clocked in with data and clock lines. I guess I could bit bang the data and clock, but wouldn't it be nice if the serial comms of the arduino could do it for me...

IIRC the Mega328 UART is not capable of sync comms.

However the SPI port is and there is the shiftOut() function, can you link to the data sheet for the chip you are using?