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參數(shù)資料
| 型號： | 9S12H256BDGV1 |
| 英文描述： | 9S12H256B Device Guide |
| 中文描述： | 9S12H256B設(shè)備指南 |
| 文件頁數(shù)： | 76/130頁 |
| 文件大?。?/td> | 2171K |
| 代理商： | 9S12H256BDGV1 |
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MC9S12H256 Device User Guide — V01.18
76
4.3 Security
The device will make available a security feature preventing the unauthorized read and write of the
memory contents. This feature allows:
Protection of the contents of FLASH,
Protection of the contents of EEPROM,
Operation in single-chip mode,
Operation from external memory with internal FLASH and EEPROM disabled.
The user must be reminded that part of the security must lie with the user’s code. An extreme example
would be user’s code that dumps the contents of the internal program. This code would defeat the purpose
of security. At the same time the user may also wish to put a back door in the user’s program. An example
of this is the user downloads a key through the SCI which allows access to a programming routine that
updates parameters stored in EEPROM.
4.3.1 Securing the Microcontroller
Once the user has programmed the FLASH and EEPROM (if desired), the part can be secured by
programming the security bits located in the FLASH module. These non-volatile bits will keep the part
secured through resetting the part and through powering down the part.
The security byte resides in a portion of the Flash array.
Check the Flash Block User Guide for more details on the security configuration.
4.3.2 Operation of the Secured Microcontroller
4.3.2.1 Normal Single Chip Mode
Thiswillbethemostcommonusageofthesecuredpart.Everythingwillappearthesameasifthepartwas
not secured with the exception of BDM operation. The BDM operation will be blocked.
4.3.2.2 Executing from External Memory
The user may wish to execute from external space with a secured microcontroller. This is accomplished
by resetting directly into expanded mode. The internal FLASH and EEPROM will be disabled. BDM
operations will be blocked.
4.3.3 Unsecuring the Microcontroller
In order to unsecure the microcontroller, the internal FLASH and EEPROM must be erased. This can be
done through an external program in expanded mode.
Once the user has erased the FLASH and EEPROM, the part can be reset into special single chip mode.
This invokes a program that verifies the erasure of the internal FLASH and EEPROM. Once this program
F
For More Information On This Product,
Go to: www.freescale.com
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PDF描述 |
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| 9S12KT256DGV1 | MC9S12KT256 Device User Guide |
| 9S12T64AF16V1 | 9S12T64 Device Guide |
| 9S12XDP512DGV1 | Device User Guide for Mask Set 0L40V ( First Silicon) |
| 9S12XDP512DGV2 | Device User Guide for Mask Set L15Y - (Second Silicon - Enhanced Feature Set) |
| 9V3 | ELEMENT 10 MICRON E MEDIA |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 9S12HN64 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:16-bit Microcontroller |
| 9S12HZ128 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:16-bit Microcontroller |
| 9S12HZ256 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:16-bit Microcontroller |
| 9S12HZ64 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:16-bit Microcontroller |
| 9S12KT256DGV1 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MC9S12KT256 Device User Guide |
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