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T89C51RD2-RDTIM 数据表(PDF) 64 Page - ATMEL Corporation |
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T89C51RD2-RDTIM 数据表(HTML) 64 Page - ATMEL Corporation |
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64 / 104 page  64 T89C51RD2 4243G–8051–05/03 Functional Description Configuration and Manufacturer Information The table below lists Configuration and Manufacturer byte information used by the boot- loader. This information can be accessed through a set of API or ISP commands. Software Security Bits (SSB) The SSB protects any Flash access from ISP command. The command "Program Software Security bit" can only write a higher priority level. There are three levels of security: • level 0: NO_SECURITY (FFh) This is the default level. From level 0, one can write level 1 or level 2. • level 1: WRITE_SECURITY (10h ) For this level it is impossible to write in the Flash memory, BSB and SBV. The Bootloader returns ’P’ on write access. From level 1, one can write only level 2. • level 2: RD_WR_SECURITY (00h The level 2 forbids all read and write accesses to/from the Flash/EEPROM memory. The Bootloader returns ’L’ on read or write access. Only a full chip erase in parallel mode (using a programmer) or ISP command can reset the software security bits. From level 2, one cannot read and write anything. Table 38. Software Security Byte Behavior Mnemonic Description Default Value BSB Boot Status Byte FFh SBV Software Boot Vector FCh SSB Software Security Byte FFh Manufacturer Id 58h Id1: Family code D7h Id2: Product Name FCh Id3: Product Revision FFh Level 0 Level 1 Level 2 Flash/EEPROM Any access allowed Read only access allowed Any access not allowed Fuse Bit Any access allowed Read only access allowed Any access not allowed BSB & SBV Any access allowed Read only access allowed Any access not allowed SSB Any access allowed Write level 2 allowed Read only access allowed |
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