AT89C51RB2 Atmel Corporation, AT89C51RB2 Datasheet - Page 90

• Manufacturer Part Number: AT89C51RB2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RB2

• Flash (kbytes): 16 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 1.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

Flash Memory Status
Figure 35. Flash Memory Possible Contents
Memory Organization
90
AT89C51RB2/RC2
0000h
7FFFh T89C51RC2 32KB
3FFFh
Default
Virgin
T89C51RB2 16KB
Table 69. Program Lock Bits of the SSB
Note:
AT89C51RB2/RC2 parts are delivered in standard with the ISP boot in the Flash mem-
ory. After ISP or parallel programming, the possible contents of the Flash memory are
summarized on Figure 35.
In the AT89C51RB2/RC2, the lowest 16K or 32K of the 64 KB program memory address
space is filled by internal Flash.
When the EA pin is high, the processor fetches instructions from internal program Flash.
Bus expansion for accessing program memory from 16K or 32K upward automatic since
external instruction fetches occur automatically when the program counter exceeds
3FFFh (16K) or 7FFFh (32K). If the EA pin is tied low, all program memory fetches are
from external memory.
After ISP
Application
Security
level
Program Lock Bits
1
2
3
U: unprogrammed or "one" level.
P: programmed or "zero" level.
X: don’t care
WARNING: Security level 2 and 3 should only be programmed after Flash and code
verification.
LB0
U
P
X
Dedicated
ISP
After ISP
Application
LB1
U
U
P
Virgin
or
Protection Description
No program lock features enabled.
ISP programming of the Flash is disabled.
Same as 2, also verify through ISP programming interface is disabled.
After Parallel
Programming
Application
After Parallel
Programming
Dedicated
ISP
Application
Virgin
or
4180E–8051–10/06