The MCU in an android headunit, including the 8227L is the overseeing Micro Controller Unit (MCU). It is a processing chip with some supporting RAM and I/O. This is a mini computer on a microchip. This microchip and its RAM is what runs android and does the control of the headunit functions.
If you have a non booting android headunit and you want to access recovery menu it can seem like an impossible task. The guides tell you to press volume buttons or tap the the power button, but what if there are no buttons?
“When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network and Amazon Associates Program, affiliate advertising programs designed to provide a means for sites to earn advertising fees by advertising and linking to Android-Headunits.com.”