AT89C5131A(2004) View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT89C5131A Datasheet PDF : 33 Pages
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Mapping and Default Value of The 4 MSB of the Hardware Byte can be read/written by software (this area is called
Hardware Security Byte
Fuse bits). The 4 LSB can only be read by software and written by hardware in parallel
mode (with parallel programmer devices).
Bit Position Mnemonic Default Value Description
7
X2B
6
BLJB
U
To start in x1 mode
P
To map the boot area in code area between F800h-FFFFh
5
OSCON1
4
OSCON0
3
reserved
2
LB2
1
LB1
U
Oscillator control (bit 1)
U
Oscillator control (bit 0)
U
P
U
To lock the chip (see datasheet)
0
LB0
U
Note: U: Unprogrammed = 1
P: Program = 0
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.
Level 0
Level 1
Level 2
Flash/EEPROM 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
4 AT89C5131A USB Bootloader
4287C–USB–11/04
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