Hi Evan,
For syntax of ECI to LLA you can use ‘eci2lla’ command as stated in the example below:
To convert the position to LLA coordinates from ECI coordinates for [-6.07 -1.28 0.66]*1e6 at 01/17/2010 10:20:36 UTC.
>>lla = eci2lla([-6.07 -1.28 0.66]*1e6,[2010 1 17 10 20 36]);
Hope this helps,
Pinkesh Narsinghani