Rainbow Electronics AT89C5132 - Manual (Page 4)

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