AT89C5115_14 Datasheet, PDF (25/113 Pages) ATMEL Corporation – Full Duplex UART Compatible 80C51

Upper 128 Bytes RAM
Expanded RAM
AT89C5115
Figure 10. Lower 128 Bytes Internal RAM Organization
7Fh
30h
2Fh _{bit-Addressable Space}
20h
(bit Addresses 0-7Fh)
1Fh
18h
10h
08h
17h _{4 Banks of}
0Fh
8 Registers
R0-R7
07h
00h
The upper 128 Bytes of RAM are accessible from address 80h to FFh using only indirect
addressing mode.
The on-chip 256 Bytes of expanded RAM (XRAM) are accessible from address 0000h to
00FFh using indirect addressing mode through MOVX instructions. In this address
range.
Note:
Lower 128 Bytes RAM, Upper 128 Bytes RAM, and expanded RAM are made of volatile
memory cells. This means that the RAM content is indeterminate after power-up and
must then be initialized properly.
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4128G–8051–02/08