AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 94

• Manufacturer Part Number: AT89C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 2
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

24.3
24.3.1
24.3.2
94
Flash Registers and Memory Map
AT89C51RD2/ED2
Hardware Register
Flash Memory Lock Bits
The AT89C51RD2/ED2 Flash memory uses several registers for its management:
The only hardware register of the AT89C51RD2/ED2 is called Hardware Byte or Hardware
Security Byte (HSB).
Table 24-1.
Boot Loader Jump Bit (BLJB)
One bit of the HSB, the BLJB bit, is used to force the boot address:
By default, this bit is programmed and the ISP is enabled.
The three lock bits provide different levels of protection for the on-chip code and data when pro-
grammed as shown in Table 24-2.
• Hardware register can only be accessed through the parallel programming modes which are
• Software registers are in a special page of the Flash memory which can be accessed through
• When this bit is programmed (‘0’ value) the boot address is F800h.
• When this bit is unprogrammed (‘1’ value) the boot address is 0000h.
Number
handled by the parallel programmer.
the API or with the parallel programming modes. This page, called "Extra Flash Memory", is
not in the internal Flash program memory addressing space.
2-0
Bit
7
6
5
4
3
X2
7
Mnemonic
XRAM
LB2-0
BLJB
Hardware Security Byte (HSB)
Bit
BLJB
X2
-
-
6
Description
X2 Mode
Programmed (‘0’ value) to force X2 mode (6 clocks per instruction) after reset.
Unprogrammed (‘1’ Value) to force X1 mode, Standard Mode, after reset (Default).
Boot Loader Jump Bit
Unprogrammed (‘1’ value) to start the user’s application on next reset at address 0000h.
Programmed (‘0’ value) to start the boot loader at address F800h on next reset (Default).
Reserved
Reserved
XRAM config bit (only programmable by programmer tools)
Programmed to inhibit XRAM.
Unprogrammed, this bit to valid XRAM (Default).
User Memory Lock Bits (only programmable by programmer tools)
See Table 24-2
5
-
4
-
XRAM
3
LB2
2
LB1
1
4235K–8051–05/08
LB0
0