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EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
00000000H to FFFFFFFFH (4 gigabytes). I/O addresses range from 00000000H to 0000FFFFH
(64 Kbytes) for programmed I/O. (See
Table 4-2. Generating A31–A0 from BE3#–BE0# and A31–A2
A31
through
Physical Address
A31
...
A31
...
A31
...
A31
...
A31
...
4.1.1.1
Memory and I/O Space Organization
The Intel486 processor datapath to memory and input/output (I/O) spaces can be 32, 16, or 8 bits
wide. The byte enable signals, BE3#–BE0#, allow byte granularity when addressing any memory
or I/O structure, whether 8, 16, or 32 bits wide.
4-2
Figure
4-1.)
Intel486™ Processor Address Signals
A2
A2
A1
A0
A2
0
0
A2
0
1
A2
1
0
A2
1
1
FFFFFFFFH
Physical
Memory
4 Gbyte
0000FFFFH
00000000H
00000000H
Physical Memory
Space
Figure 4-1. Physical Memory and I/O Spaces
BE3#
BE2#
BE1#
X
X
X
X
X
0
0
1
Not
Accessible
Not
Accessible
Accessible
Programmed
64 Kbyte
I/O Space
I/O Space
BE0#
X
0
0
1
1
1
1
1
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