MC9S12G FREESCALE [Freescale Semiconductor, Inc], MC9S12G Datasheet - Page 756

• Manufacturer Part Number: MC9S12G
• Description: Ignores external trigger. Performs one conversion sequence and stops.
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

32 KByte Flash Module (S12FTMRG32K1V1)
The user code stored in the P-Flash memory must have a method of receiving the backdoor keys from an
external stimulus. This external stimulus would typically be through one of the on-chip serial ports.
If the KEYEN[1:0] bits are in the enabled state (see
backdoor key access sequence described below:
The Verify Backdoor Access Key command is monitored by the Memory Controller and an illegal key will
prohibit future use of the Verify Backdoor Access Key command. A reset of the MCU is the only method
to re-enable the Verify Backdoor Access Key command. The security as defined in the Flash security byte
(0x3_FF0F) is not changed by using the Verify Backdoor Access Key command sequence. The backdoor
keys stored in addresses 0x3_FF00-0x3_FF07 are unaffected by the Verify Backdoor Access Key
command sequence. The Verify Backdoor Access Key command sequence has no effect on the program
and erase protections defined in the Flash protection register, FPROT.
After the backdoor keys have been correctly matched, the MCU will be unsecured. After the MCU is
unsecured, the sector containing the Flash security byte can be erased and the Flash security byte can be
reprogrammed to the unsecure state, if desired. In the unsecure state, the user has full control of the
contents of the backdoor keys by programming addresses 0x3_FF00-0x3_FF07 in the Flash configuration
field.
22.5.2
A secured MCU can be unsecured in special single chip mode by using the following method to erase the
P-Flash and EEPROM memory:
If the P-Flash and EEPROM memory are verified as erased, the MCU will be unsecured. All BDM
commands will now be enabled and the Flash security byte may be programmed to the unsecure state by
continuing with the following steps:
756
1. Follow the command sequence for the Verify Backdoor Access Key command as explained in
2. If the Verify Backdoor Access Key command is successful, the MCU is unsecured and the
1. Reset the MCU into special single chip mode
2. Delay while the BDM executes the Erase Verify All Blocks command write sequence to check if
3. Send BDM commands to disable protection in the P-Flash and EEPROM memory
4. Execute the Erase All Blocks command write sequence to erase the P-Flash and EEPROM
5. After the CCIF flag sets to indicate that the Erase All Blocks operation has completed, reset the
6. Delay while the BDM executes the Erase Verify All Blocks command write sequence to verify that
7. Send BDM commands to execute the Program P-Flash command write sequence to program the
This document is valid for the S12G96 and the S12G128 device. All information related to other devices is preliminary.
Section 22.4.6.11
SEC[1:0] bits in the FSEC register are forced to the unsecure state of 10
the P-Flash and EEPROM memories are erased
memory. Alternatively the Unsecure Flash command can be executed, if so the steps 5 and 6 below
are skeeped.
MCU into special single chip mode
the P-Flash and EEPROM memory are erased
Flash security byte to the unsecured state
Unsecuring the MCU in Special Single Chip Mode using BDM
MC9S12G Family Reference Manual,
Section
22.3.2.2), the MCU can be unsecured by the
Rev.1.01
Freescale Semiconductor