AT89C51SND1_06 ATMEL [ATMEL Corporation], AT89C51SND1_06 Datasheet - Page 4

• Manufacturer Part Number: AT89C51SND1_06
• Description: USB Microcontrollers
• Manufacturer: ATMEL [ATMEL Corporation]

Security
4
AT89C51SND1
The bootloader has Software Security Byte (SSB see
or ISP access.
The Software Security Byte (SSB) protects from ISP accesses. The command ‘Program Soft-
ware Security Bit’ can only write a higher priority level. There are three levels of security:
•
•
•
Only a full chip erase command can reset the software security bits.
Table 3. Security Levels
Flash
Fuse bit
BSB & SBV & EB
SSB
Manufacturer info
Bootloader info
Erase block
Full chip erase
Blank Check
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.
Level 0
Any access allowed
Any access allowed
Any access allowed
Any access allowed
Read only access allowed
Read only access allowed
Allowed
Allowed
Allowed
Level 1
Read only access allowed
Read only access allowed
Any access allowed
Write level2 allowed
Read only access allowed
Read only access allowed
Not allowed
Allowed
Allowed
Table
7) to protect itself from user access
Level 2
All access not allowed
All access not allowed
Any access allowed
Read only access allowed
Read only access allowed
Read only access allowed
Not allowed
Allowed
Allowed
4254C–MP3–03/06