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TSC80251G2D-24CB 参数 Datasheet PDF下载

TSC80251G2D-24CB图片预览
型号: TSC80251G2D-24CB
PDF下载: 下载PDF文件 查看货源
内容描述: 8位/ 16位微控制器,串行通信接口 [8/16-bit Microcontroller with Serial Communication Interfaces]
分类和应用: 微控制器外围集成电路异步传输模式ATM通信时钟
文件页数/大小: 63 页 / 813 K
品牌: TEMIC [ TEMIC SEMICONDUCTORS ]
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TSC80251G2D  
8.2.1 Lock Bit System  
The TSC87251G2D products implement 3 levels of security for User’s program as described in Table 35. The  
TSC83251G2D products implement only the first level of security.  
Level 0 is the level of an erased part and does not enable any security features.  
Level 1 locks the programming of the User’s internal Code Memory, the Configuration Bytes and the Encryption  
Array.  
Level 2 locks the verifying of the User’s internal Code Memory. It is always possible to verify the Configuration  
Bytes and the Lock Bits. It is never possible to verify the Encryption Array.  
Level 3 locks the external execution.  
Table 35. Lock Bits Programming  
External  
Lock bits  
LB[2:0]  
Internal  
External  
Level  
Verification  
Programming  
PROM read  
(MOVC)  
Execution  
Execution  
(1)  
(2)  
0
1
2
3
000  
001  
Enable  
Enable  
Enable  
Enable  
Enable  
Enable  
Enable  
Disable  
Enable  
Enable  
Disable  
Disable  
Disable  
Enable  
(1)  
Enable  
Disable  
Disable  
Disable  
(3)  
01x  
Disable  
Disable  
(3)  
1xx  
Notes:  
1. Returns encrypted data if Encryption Array is programmed.  
2. Returns non encrypted data.  
3. x means don’t care. Level 2 always enables level 1, and level 3 always enables levels 1 and 2.  
The security level may be verified according to Table 36.  
Table 36. Lock Bits Verifying  
Level  
Lock bits Data(1)  
0
1
2
3
xxxxx000  
xxxxx001  
xxxxx01x  
xxxxx1xx  
Note:  
1. x means don’t care.  
8.2.2 Encryption Array  
The TSC83251G2D and TSC87251G2D products include a 128-byte Encryption Array located in non-volatile  
memory outside the memory address space. During verification of the on-chip code memory, the seven low-order  
address bits also address the Encryption Array. As the byte of the code memory is read, it is exclusive-NOR’ed  
(XNOR) with the key byte from the Encryption Array. If the Encryption Array is not programmed (still all 1s),  
the user program code is placed on the data bus in its original, unencrypted form. If the Encryption Array is  
programmed with key bytes, the user program code is encrypted and cannot be used without knowledge of the  
key byte sequence.  
To preserve the secrecy of the encryption key byte sequence, the Encryption Array can not be verified.  
Cautions:  
1. When a MOVC instruction is executed, the content of the ROM is not encrypted. In order to fully protect the user program code, the lock  
bit level 1 (see Table 35) must always be set when encryption is used.  
2. If the encryption feature is implemented, the portion of the on-chip code memory that does not contain program code should be filled with  
“random” byte values to prevent the encryption key sequence from being revealed.  
29  
Rev. A - May 7, 1999  
 
 
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