参数资料
型号: MC56F8347MPY60
厂商: FREESCALE SEMICONDUCTOR INC
元件分类: 数字信号处理
英文描述: 16-BIT, 120 MHz, OTHER DSP, PQFP160
封装: LQFP-160
文件页数: 27/172页
文件大小: 2202K
代理商: MC56F8347MPY60
56F8347 Technical Data, Rev. 5.0
122
Freescale Semiconductor
Preliminary
Part 7 Security Features
The 56F8347/56F8147 offer security features intended to prevent unauthorized users from reading the
contents of the Flash Memory (FM) array. The Flash security consists of several hardware interlocks that
block the means by which an unauthorized user could gain access to the Flash array.
However, 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, as this code would defeat the purpose of security. At the same
time, the user may also wish to put a “backdoor” in his program. As an example, the user downloads a
security key through the SCI, allowing access to a programming routine that updates parameters stored in
another section of the Flash.
7.1 Operation with Security Enabled
Once the user has programmed the Flash with his application code, the device can be secured by
programming the security bytes located in the FM configuration field, which occupies a portion of the FM
array. These non-volatile bytes will keep the part secured through reset and through power-down of the
device. Only two bytes within this field are used to enable or disable security. Refer to the Flash Memory
section in the 56F8300 Peripheral User Manual for the state of the security bytes and the resulting state
of security. When Flash security mode is enabled in accordance with the method described in the Flash
Memory module specification, the device will disable external P-space accesses (disabling EXTBOOT =
1 mode), restrict memory and disable the core EOnCE debug capabilities. Normal program execution is
otherwise unaffected.
7.2 Flash Access Blocking Mechanisms
The 56F8347/56F8147 have several operating functional and test modes. Effective Flash security must
address operating mode selection and anticipate modes in which the on-chip Flash can be compromised
and read without explicit user permission. Methods to block these are outlined in the next subsections.
7.2.1
Forced Operating Mode Selection
At boot time, the SIM determines in which functional modes the device will operate. These are:
Internal Boot Mode
External Boot Mode
Secure Mode
When Flash security is enabled as described in the Flash Memory module specification, the device will
boot in internal boot mode, disable all access to external P-space, and start executing code from the Boot
Flash at address 0x02_0000.
This security affords protection only to applications in which the device operates in internal Flash security
mode. Therefore, the security feature cannot be used unless all executing code resides on-chip.
When security is enabled, any attempt to override the default internal operating mode by asserting the
EXTBOOT pin in conjunction with reset will be ignored.
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