at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 28

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Physical memory
organisation
On-Chip Flash memory
28
AT89C51RE2
Figure Physical memory organisation
The AT89C51RE2 implements up to 128K bytes of on-chip program/code memory.
Figure 1 and Figure 2. shows the partitioning of internal and external program/code
memory spaces according to EA value.
The memory partitioning of the 8051 core microcontroller is typical a Harvard architec-
ture where program and data areas are held in separate memory areas. The program
and data memory areas use the same physical address range from 0000H-FFFFH and
a 8 bit instruction code/data format.
To access more than 64kBytes of code memory, without mofications of the MCU core,
and developement tools, the bank switching method is used.
The internal program memory is expanded to 128kByte in the´Expanded Configuration’,
the data memory remains in the ´Normal Configuration´. The program memory is splited
into four 32 kByte banks (named Bank 0-2). The MCU core still addresses up to
64kBytes where the upper 32Kbytes can be selected between 3 32K bytes bank of on-
chip flash memory. The lower 32K bank is used as common area for interrupt subrou-
tines, bank switching and funtions calls between banks.
The AT89C51RE2 also implements an extra upper 32K bank (Bank3) that allows exter-
nal code execution.
Fuse Configuration Byte(1 byte)
Extra Row FM0 (128 bytes)
Hardware Security (1 byte)
Column Latches (128 bytes)
1FFFFh
00000h
FCB
HSB
Flash memory
128K bytes
user space
FM0
4K bytes
ROM
RM0
7663B–8051–03/07