Hi Ricardo,
This is a "one way" conversion only;
Autonomous to LWAPP (Yes)
LWAPP to Autonomous (No)
Converting an Autonomous AP521 Using the CCA
When an autonomous AP521 access point is converted to controller-mode operation using the CCA, the access point properties screen continues to indicate that the access point is an AIR-AP521G-A-K9 after the conversion. This is in agreement with the product label on the access point. However, the CCA displays a small triangle icon next to the converted access point to indicate that the access point is now operating as a controller-mode access point.
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Note The CCA conversion process is one-way. Once the conversion takes place, you cannot restore the access point to autonomous operation.
http://www.cisco.com/en/US/docs/wireless/controller/release/notes/c526rn42614.html#wp245163
Hope this helps!
Rob