AT89C51ID2-SMSIM ATMEL [ATMEL Corporation], AT89C51ID2-SMSIM Datasheet - Page 127

• Manufacturer Part Number: AT89C51ID2-SMSIM
• Description: 8-bit Flash Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

Functional Description
Software Security Bits (SSB)
Table 93. Software Security Byte Behavior
4289A–8051–09/03
Manufacturer info
Bootloader info
Full chip erase
Flash/EEprom
Blank Check
BSB & SBV
Erase block
Fuse bit
SSB
Read only access allowed
Read only access allowed
Any access allowed
Any access allowed
Any access allowed
Any access allowed
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:
•
This is the default level.
From level 0, one can write level 1 or level 2.
•
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.
•
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.
Level 0
Allowed
Allowed
Allowed
level 0: NO_SECURITY (FFh)
level 1: WRITE_SECURITY (FEh )
level 2: RD_WR_SECURITY (FCh
Read only access allowed
Read only access allowed
Read only access allowed
Read only access allowed
Read only access allowed
Write level 2 allowed
Not allowed
Level 1
Allowed
Allowed
Read only access allowed
Read only access allowed
Read only access allowed
Any access not allowed
Any access not allowed
Any access not allowed
AT89C51ID2
Not allowed
Level 2
Allowed
Allowed
127