t89c51rd2-slscl ATMEL Corporation, t89c51rd2-slscl Datasheet - Page 64

• Manufacturer Part Number: t89c51rd2-slscl
• Description: 0 To 40 Mhz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

Functional Description
Configuration and
Manufacturer Information
Software Security Bits (SSB)
64
T89C51RD2
The table below lists Configuration and Manufacturer byte information used by the boot-
loader. This information can be accessed through a set of API or ISP commands.
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.
Table 38. Software Security Byte Behavior
Mnemonic
BSB
SBV
SSB
Manufacturer Id
Id1: Family code
Id2: Product Name
Id3: Product Revision
Flash/EEPROM
BSB & SBV
level 0: NO_SECURITY (FFh)
level 1: WRITE_SECURITY (10h )
level 2: RD_WR_SECURITY (00h
Fuse Bit
SSB
Any access allowed
Any access allowed
Any access allowed
Any access allowed
Description
Boot Status Byte
Software Boot Vector
Software Security Byte
Level 0
Read only access allowed
Read only access allowed
Read only access allowed
Write level 2 allowed
Level 1
Read only access allowed
Any access not allowed
Any access not allowed
Any access not allowed
Default Value
Level 2
4243G–8051–05/03
FCh
FCh
FFh
FFh
D7h
FFh
58h