Lpc2000

--- In lpc2000@yahoogroups.com, "Sutton Mehaffey" <sutton@...> wrote:
>
> 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
>

You can get the specifications for the I2C protocol here:
http://www.semiconductors.philips.com/acrobat_download/literature/9398/39340011.pdf

Regarding SCL, the quick answer is that SCL remains high unless there
is an actual transfer in progress. The phasing of SCL and SDA
transitions define the start/stop conditions of the bus. 

-- Dave