Freescale Semiconductor Demonstration Board for Freescale MC9S12XHY256 Microcontroller DEMO9S12XHY256 DEMO9S12XHY256 Manual De Usuario

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Freescale Semiconductor

). The Verify Backdoor Access Key command must not be executed from the Flash block

containing the backdoor comparison key to avoid code runaway.

Upon clearing CCIF to launch the Verify Backdoor Access Key command, the Memory Controller will
check the FSEC KEYEN bits to verify that this command is enabled. If not enabled, the Memory
Controller sets the ACCERR bit in the FSTAT register and terminates. If the command is enabled, the
Memory Controller compares the key provided in FCCOB to the backdoor comparison key in the Flash
configuration field with Key 0 compared to 0x7F_FF00, etc. If the backdoor keys match, security will be
released. If the backdoor keys do not match, security is not released and all future attempts to execute the
Verify Backdoor Access Key command are aborted (set ACCERR) until a reset occurs. The CCIF flag is
set after the Verify Backdoor Access Key operation has completed.

The Set User Margin Level command causes the Memory Controller to set the margin level for future read
operations of a specific P-Flash or D-Flash block.

000

0x0C

Not required

001

Key 0

010

Key 1

011

Key 2

100

Key 3

FSTAT

ACCERR

Set if CCOBIX[2:0] != 100 at command launch

Set if an incorrect backdoor key is supplied

Set if backdoor key access has not been enabled (KEYEN[1:0] != 10, see

)

Set if the backdoor key has mismatched since the last reset

FPVIOL

None

MGSTAT1

None

MGSTAT0

None

000

0x0D

Global address [22:16] to identify the

Flash block

001

Margin level setting