Motorola ColdFire MCF5281 - Manual (Page 134)

ColdFire Flash Module (CFM)
6-22 Freescale Semiconductor
6.4.5 Master Mode
If the MCU is booted in master mode with an external memory selected as the boot device, the CFM will
not respond to the first transfer request out of reset. This will allow the external boot device to provide the
reset vector and terminate the bus cycle.
6.5 Flash Security Operation
The CFM array provides security information to the integration module and the rest of the MCU. A
longword in the Flash configuration field stores this information. This longword is read automatically after
each reset and is stored in the CFMSEC register.
NOTE
Enabling Flash security will disable BDM communications.
NOTE
When Flash security is enabled, the chip will boot in single chip mode
regardless of the external reset configuration.
In user mode, security can be bypassed via a back door access scheme using an 8-byte long key. Upon
successful completion of the back door access sequence, the module output signal and status bit indicating
that the chip is secure are cleared.
The CFM may be unsecured via one of two methods:
1. Executing a back door access scheme.
2. Passing an erase verify check.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3