SLAA450G April 2010 – April 2020
When protected, the BSL memory cannot be read or jumped into from a location external to BSL memory. This protection makes the BSL more secure against erase and also prevents erroneous BSL execution. However, if the entire BSL memory space were protected in this way, it would also mean that user application code could not call the BSL in any way, such as an intentional BSL start-up or using certain public BSL functions.
The Z-Area is a special section of memory designed to allow for a protected BSL to be publically accessible in a controlled way. The Z-Area is a section of BSL memory between addresses 0x1000 and 0x100F that can be jumped to and read from external application code. The Z-Area functions as a gateway from which a jump can be performed to any location within the BSL memory. The default TI BSL uses this area for jumps to the start of the BSL and for jumps into BSL public functions.