AT89C51AC3 Atmel Corporation, AT89C51AC3 Datasheet - Page 4

• Manufacturer Part Number: AT89C51AC3
• Manufacturer: Atmel Corporation

Specifications of AT89C51AC3

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 62.5
• Sram (kbytes): 2.25
• Eeprom (bytes): 2048
• Self Program Memory: API
• Operating Voltage (vcc): 3.0 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

Security
Software Boot
Vector
4
AT89C51AC3 UART Bootloader
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 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.
The Software Boot Vector (SBV) forces the execution of a user bootloader starting at address
[SBV]00h in the application area (FM0).
The way to start this user bootloader is described in the section “Boot Process”.
Application
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, BSB and SBV.
The Bootloader returns an error message.
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 error message.
Flash/EEPROM
Fuse bit
BSB & SBV & EB Any access allowed
SSB
Manufacturer info Read only access allowed
Bootloader info
Erase block
Full chip erase
Blank Check
User Bootloader
Any access allowed
Any access allowed
Any access allowed
Read only access allowed
Allowed
Allowed
Allowed
FM0
Level 0
[SBV]00h
Read only access allowed
Read only access allowed
Read only access allowed
Write level2 allowed
Read only access allowed
Read only access allowed
Not allowed
Allowed
Allowed
Level 1
UART Bootloader
FM1
All access not allowed
All access not allowed
All access not allowed
Read only access allowed
Read only access allowed
Read only access allowed
Not allowed
Allowed
Allowed
Level 2
4386B–8051–03/08