at89c51ac3-s3sim ATMEL Corporation, at89c51ac3-s3sim Datasheet - Page 20

• Manufacturer Part Number: at89c51ac3-s3sim
• Description: At89c51ac3 Enhanced 8-bit Microcontroller With 64kb Flash Memory
• Manufacturer: ATMEL Corporation

Data Memory
20
AT89C51AC3
The AT89C51AC3 provides data memory access in two different spaces:
1. The internal space mapped in three separate segments:
•
•
•
2. The external space.
A fourth internal segment is available but dedicated to Special Function Registers,
SFRs, (addresses 80h to
Figure 8 shows the internal and external data memory spaces organization.
Figure 7. Internal Memory - RAM
Figure 8. Internal and External Data Memory Organization ERAM-XRAM
the lower 128 Bytes RAM segment.
the upper 128 Bytes RAM segment.
the expanded 2048 Bytes RAM segment (ERAM).
00h
256 up to 2048 Bytes
Internal ERAM
Internal
EXTRAM = 0
FFh
7Fh
FFh
80h
00h
) accessible by direct addressing mode.
indirect addressing
direct or indirect
Internal RAM
Internal RAM
addressing
128 Bytes
128 Bytes
Upper
Lower
FFh or 7FFh
FFh
80h
direct addressing
FFFFh
0000h
Registers
Function
Special
External XRAM
External
EXTRAM = 1
64K Bytes
4383D–8051–02/08