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A–20
System Address Space
PCI Sparse Memory Space
Table 1–6 defines the low-order PCI sparse memory address bits. Signals
addr_h<7:3> are used to generate the length of the PCI transaction in bytes, the byte
enable bits, and ad<2:0>. The 21164 signals addr_h<30:8> correspond to the quad-
word PCI address and are sent out on ad<25:3>.
1
Byte enable set to 0 indicates that byte lane carries meaningful data
.
2
A<7> = addr_h<7>
.
3
In PCI sparse memory space, ad<1:0> is always zero.
4
Missing entries (for example, word size with 21164 address = 11) enjoy UNPREDICTABLE results.
Table 1–6 PCI Memory Sparse-Space Read/Write Encodings
Size Byte Offset
addr_h
<6:5>
21164
Instruction
Allowed
ad<2:0>
PCI Byte
Enable
1
Data-In Register
Byte Lanes
63.....32 31.......0
addr_h<4:3>
00
A<7>
2
,00
3
1110
OOOX
01
A<7>,00
1101
OOXO
Byte
00
10
LDL,STL
A<7>,00
1011
OXOO
11
A<7>,00
0111
XOOO
00
A<7>,00
1100
OOXX
Word
4
01
01
LDL,STL
A<7>,00
1001
OXXO
10
A<7>,00
0011
XXOO
00
A<7>,00
1000
OXXX
Tribyte
10
01
LDL,STL
A<7>,00
0001
XXXO
Longword
11
00
LDL,STL
A<7>,00
0000
XXXX
Quadword
11
11
LDQ,STQ
000
0000
XXXX XXXX