mc68hc908lv8 Freescale Semiconductor, Inc, mc68hc908lv8 Datasheet - Page 192

• Manufacturer Part Number: mc68hc908lv8
• Description: M68hc08 Microcontrollers 8-bit Microcontroller With Integrated Lcd Driver
• Manufacturer: Freescale Semiconductor, Inc

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16.3.3 Extended Security
In addition to the above security, a more secure feature called extended security is implemented in the
MCU to further protect FLASH contents. Once this extended security is enabled, the MCU does not allow
any user to enter the monitor mode even when all 8 security bytes are matched correctly. The extended
security feature can be enabled by programming address $FDFF located in the user FLASH memory with
data $00.
To unlock the extended security feature, the MCU must enter the monitor mode by failing the 8 byte
security check. Then the FLASH must be mass-erased. This unlock process will erase the FLASH
contents completely.
16.4 Routines Supported in ROM
In the ROM, five routines are supported. Because the ROM has a jump table, the user does not call the
routines with direct addresses. Therefore, the calling addresses will not change—even when the ROM
code is updated in the future.
This section introduces each routine briefly. Details are discussed in later sections.
16.4.1 Variables Used in the Routines
The Copy2RAM, rErase, and rProgram routines require certain registers and/or RAM locations to be
initialized before calling the routines in the user software.
and their locations.
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GetByte — This routine is used to receive a byte serially on the general-purpose I/O PTA0. The
receiving baud rate is the same as the baud rate used in monitor mode.
PutByte — This routine is used to send a byte serially on the general-purpose I/O PTA0. The
sending baud rate is the same as the baud rate specified in monitor mode.
Copy2RAM — This routine is used to copy data in a contiguous range of FLASH locations to the
DATA array assigned in RAM. The user can choose the DATA array locations and the variable
locations required for this routine in the user software.
rErase — This routine is used to erase either a page (64 bytes) or the whole array of FLASH. The
user can choose the variable locations required for this routine in the user software. It can be used
when the internal operating frequency (f
rProgram — This routine is used to program a contiguous range of FLASH locations.
Programming data is first loaded into the DATA array assigned in RAM. The user can choose the
DATA array locations and the variable locations required for this routine in the user software.
rProgram can be used when the internal operating frequency (f
To avoid enabling the extended security unintentionally, the user must
make sure that the user software does not contain data $00 at address
$FDFF.
MC68HC908LV8 Data Sheet, Rev. 2
op
) is between 1.5 MHz and 8.0 MHz.
NOTE
Table 16-9
shows variables used in the routines
op
) is between 1.5 MHz and 8.0 MHz.
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