mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 179

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8 Security
8.6 Unsecuring the MCU using the Erase All Blocks
command
The Erase All Blocks operation erases the entirety of the program flash memory,
FlexNVM, and FlexRAM used as EEPROM; verifies the erase; and then releases MCU
security.
When the chip is in BDM, the functionality of the Erase All Blocks command is also
available in an uncommanded fashion using the DGBCR[0] bit. When invoked, this
function erases all program flash memory, FlexNVM, and FlexRAM used as EEPROM
regardless of the protection settings. This function, like the normal command activation,
also initializes all locations in the FlexRAM used as EEPROM to the address FFFFh. If
the Flash Erase Verify passes, the routine then releases security by setting the
FSEC[SEC] field to the unsecure state.
8.7 Security Interactions with other Modules
The flash security settings will be used by the SoC to determine what resources are
available. The following sections describe the interactions between modules and the flash
security settings or the impact that the flash security has on non-flash modules.
8.7.1 Security interactions with Mini-FlexBus
If flash security is enabled, the SOPT6[MBSL] field in the SIM enables/disables off-chip
accesses through the Mini-FlexBus interface. The field controls whether both instruction
accesses and data accesses are allowed, whether both instruction accesses and data
accesses are disallowed, or whether instruction accesses are disallowed while data
accesses are allowed.
8.7.2 Security interactions with EzPort
When flash memory security is active, the MCU can still boot in EzPort mode. The
EzPort module can execute an erase all blocks command (mass erase). The mass erase
can be used to disable flash memory security, but all of the flash memory's contents are
lost in the process.
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Preliminary
Freescale Semiconductor, Inc.
179