Lpc2000

Can someone unconfuse me on several I2C issues as I try to understand
the Philips I2C code in the file section?

On, my design using a LPC2148, I am using Master Transmitter mode to
address a RAM.

The AA flag: Is it only used to acknowledge data received from the RAM
after reading from I2C0DAT?  I assume that the ACKs received from the
RAM when simply addressing it is not related to AA (but is the SI
bit).  I noticed in the Philips code that the only AA assertion is
done after receiving data from the chip.  I also assume that the slave
will always give an ACK after sending it data (by the SI flag).  Or,
am I totally off base?

Also, does SCL run all the time, or just during the data transfer? 
I'm not seeing a SCL signal at all when I start my code.

Thanks.

Sutton