Rainbow-electronics AT89C5132 Manual do Utilizador descarregar pdf (Página 4)

AT89C5132

4256A–USB–06/03

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.

The Bootloader returns an err_WRITE status.

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 err_WRITE or an err_VENDOR status.

Only a full chip erase command can reset the software security bits.

Table 3. Security Levels

Level 0 Level 1 Level 2

Flash 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 Any access allowed Any access 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

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