at89c51rd2-smsum ATMEL Corporation, at89c51rd2-smsum Datasheet - Page 97

• Manufacturer Part Number: at89c51rd2-smsum
• Description: 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

24.4
Figure 24-1. Flash Memory Possible Contents
24.5
24.6
24.6.1
4235J–8051–01/08
Flash Memory Status
Memory Organization
Bootloader Architecture
FFFFh
0000h
Introduction
Default
Virgin
Table 24-5.
Note:
AT89C51RD2/ED2 parts are delivered in standard with the ISP ROM bootloader.
After ISP or parallel programming, the possible contents of the Flash memory are summarized in
Figure 24-1:
When the EA pin is high, the processor fetches instructions from internal program Flash. If the
EA pin is tied low, all program memory fetches are from external memory.
The bootloader manages communication according to a specifically defined protocol to provide
the whole access and service on Flash memory. Furthermore, all accesses and routines can be
called from the user application.
Security
Level
Program Lock Bits
1
2
3
After ISP
Application
X: Do not care
WARNING: Security level 2 and 3 should only be programmed after Flash verification.
LB0
X
1
0
User Memory Lock Bits of the SSB
LB1
1
1
0
Dedicated
ISP
After ISP
Application
Virgin
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.
or
After Parallel
Programming
Application
After Parallel
Programming
Dedicated
ISP
Application
Virgin
AT89C51RD2/ED2
or
After Parallel
Programming
Application
Virgin
or
97