user manual

8XC251SA, SB, SP, SQ USER’S MANUAL
3-4
Figure 3-3. Address Space Mappings MCS
®
51 Architecture to MCS
®
251 Architecture
Table 3-1. Address Mappings
Memory Type
MCS
®
51 Architecture MCS
®
251 Architecture
Size Location
Data
Addressing
Location
Code 64 Kbytes 0000H–FFFFH
Indirect using
MOVC instr.
FF:0000H–FF:FFFFH
External Data 64 Kbytes 0000H–FFFFH
Indirect using
MOVX instr.
01:0000H–01:FFFFH
Internal Data
128 bytes 00H–7FH Direct, Indirect 00:0000H–00:007FH
128 bytes 80H–FFH Indirect 00:0080H–00:00FFH
SFRs 128 bytes S:80H–S:FFH Direct S:080H–S:0FFH
Register File 8 bytes R0–R7 Register R0–R7

FFH
SFR Space
512 Bytes
Memory Address Space
16 Mbytes
S:000H
MCS

51 Architecture
Code Memory
MCS 51 Architecture
External Data Memory
MCS 51 Architecture
Internal Data Memory
FFFFH
00H
0000H
FFFFH
0000H
MCS 51 Architecture
SFRs
00:0000H
01:0000H
02:0000H
FF:0000H
A4133-01
S:100H
S:1FFH
8
Register File
64 Bytes
MCS 51 Architecture R. F.
0
0
63
S:07FH
80H
FFH
7