EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
4-2
00000000H to FFFFFFFFH (4 gigabytes). I/O addresses range from 00000000H to 0000FFFFH
(64 Kbytes) for programmed I/O. (See Figure 4-1.)
Figure 4-1. Physical Memory and I/O Spaces
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.
Table 4-2. Generating A31–A0 from BE3#–BE0# and A31–A2
Intel486™ Processor Address Signals
A31 through A2
BE3# BE2# BE1# BE0#
Physical Address
A31 ... A2 A1 A0
A31...A200XXX0
A31...A201XX01
A31...A210X011
A31...A2110111
Physical
Memory
4 Gbyte
Not
Accessible
64 Kbyte
{
Accessible
Programmed
I/O Space
0000FFFFH
00000000H
00000000H
Physical Memory
Space
I/O Space
FFFFFFFFH
Not
Accessible
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