MM912H634CV1AE Freescale Semiconductor, MM912H634CV1AE Datasheet - Page 325

• Manufacturer Part Number: MM912H634CV1AE
• Description: 64KS12 LIN2xLS/HS Isense
• Manufacturer: Freescale Semiconductor
• Series: -r

Specifications of MM912H634CV1AE

• Applications: Automotive
• Core Processor: HCS12
• Program Memory Type: FLASH (64 kB)
• Controller Series: HCS12
• Ram Size: 6K x 8
• Interface: LIN
• Number Of I /o: -
• Voltage - Supply: 5.5 V ~ 27 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.40.5.1
The MCU may be unsecured by using the backdoor key access feature which requires knowledge of the contents of the backdoor
keys (four 16-bit words programmed at addresses 0x3_FF00-0x3_FF07). If the KEYEN[1:0] bits are in the enabled state (see
Section
prospective keys for comparison to the keys stored in the Flash memory via the Memory Controller. If the keys presented in the
Verify Backdoor Access Key command match the backdoor keys stored in the Flash memory, the SEC bits in the FSEC register
(see
While the Verify Backdoor Access Key command is active, P-Flash memory and D-Flash memory will not be available for read
access and will return invalid data.
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
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.
4.40.5.2
A secured MCU can be unsecured in special single chip mode by using the following method to erase the P-Flash and D-Flash
memory:
If the P-Flash and D-Flash 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:
4.40.5.3
The availability of Flash module commands depends on the MCU operating mode and security state as shown in
4.40.6
On each system reset the Flash module executes a reset sequence which establishes initial values for the Flash Block
Configuration Parameters, the FPROT and DFPROT protection registers, and the FOPT and FSEC registers. The Flash module
reverts to using built-in default values that leave the module in a fully protected and secured state if errors are encountered during
Freescale Semiconductor
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Table
4.40.3.2.2), the Verify Backdoor Access Key command (see
Follow the command sequence for the Verify Backdoor Access Key command as explained in
If the Verify Backdoor Access Key command is successful, the MCU is unsecured and the SEC[1:0] bits in the FSEC
register are forced to the unsecure state of 10
Reset the MCU into special single chip mode
Delay while the BDM executes the Erase Verify All Blocks command write sequence to check if the P-Flash and D-Flash
memories are erased
Send BDM commands to disable protection in the P-Flash and D-Flash memory
Execute the Erase All Blocks command write sequence to erase the P-Flash and D-Flash memory
After the CCIF flag sets to indicate that the Erase All Blocks operation has completed, reset the MCU into special single
chip mode
Delay while the BDM executes the Erase Verify All Blocks command write sequence to verify that the P-Flash and
D-Flash memory are erased
Send BDM commands to execute the Program P-Flash command write sequence to program the Flash security byte to
the unsecured state
Reset the MCU
414) will be changed to unsecure the MCU. Key values of 0x0000 and 0xFFFF are not permitted as backdoor keys.
Initialization
Unsecuring the MCU using Backdoor Key Access
Unsecuring the MCU in Special Single Chip Mode using BDM
Mode and Security Effects on Flash Command Availability
MM912_634 Advance Information, Rev. 4.0
Section
4.40.3.2.2), the MCU can be unsecured by the backdoor key access
Section
4.40.4.5.11) allows the user to present four
Section 4.40.4.5.11
Table
445.
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