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AT89C51AC2 Datasheet(PDF) 4 Page - ATMEL Corporation |
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AT89C51AC2 Datasheet(HTML) 4 Page - ATMEL Corporation |
4 / 29 page 4 A/T89C51AC2 UART Bootloader 4231C–CAN–03/05 Mapping and Default Value of Hardware Security Byte The 4 Most Significant Byte (MSB) of the Hardware Byte can be read/written by soft- ware (this area is called Fuse bits). The 4 Least Significant Byte (LSB) can only be read by software and written by hardware in parallel mode (with parallel programmer devices). Note: U: Unprogram = 1 P: Program = 0 Security The bootloader has Software Security Byte (SSB) to protect itself from user access or ISP access. The Software Security Byte (SSB) protects from ISP accesses. 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 (FEh) In this level it is impossible to write in the Flash memory, BSB and SBV. The Bootloader returns an error message. From level 1, one can write only level 2. • level 2: RD_WR_SECURITY (FCh) Level 2 forbids all read and write accesses to/from the Flash memory. The Bootloader returns an error message. Only a full chip erase command can reset the software security bits. Bit Position Mnemonic Default Value Description 7 X2B U To start in x1 mode 6 BLJB P To map the boot area in code area between F800h-FFFFh 5 Reserved U 4 Reserved U 3 Reserved U 2LB2 P To lock the chip (see datasheet) 1LB1 U 0LB0 U Level 0 Level 1 Level 2 Flash/EEPROM Any access allowed Read only access allowed All access not allowed Fuse bit Any access allowed Read only access allowed All access not allowed BSB & SBV & EB Any access allowed Read only access allowed All access not allowed SSB Any access allowed Write level2 allowed Read only access allowed Manufacturer info Read only access allowed Read only access allowed Read only access allowed Bootloader info Read only access allowed Read only access allowed Read only access allowed Erase block Allowed Not allowed Not allowed Full chip erase Allowed Allowed Allowed Blank Check Allowed Allowed Allowed |
Similar Part No. - AT89C51AC2_05 |
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Similar Description - AT89C51AC2_05 |
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