10. Endian Mapping
178
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
illustrates the lanes used to carry each byte of a multi-byte structure on a 64-bit PB Interface
data bus.
PowerSpan II supports both big-endian and PowerPC little-endian byte ordering. Endian selection with
PowerPC is performed with the processor register MSR[LE] and defaults to big-endian. PowerPC
little-endian mode allows a PowerPC and Pentium processor to share a data structure in memory.
001
1
P1_AD[15:8]
0
1
Px_AD[15:8]
010
2
P1_AD[23:16]
0
2
Px_AD[23:16]
011
3
P1_AD[31:24]
0
3
Px_AD[31:24]
100
4
P1_AD[39:32]
1
0
Px_AD[7:0]
101
5
P1_AD[47:40]
1
1
Px_AD[15:8]
110
6
P1_AD[55:48]
1
2
Px_AD[23:16]
111
7
P1_AD[63:56]
1
3
Px_AD[31:24]
Table 47: 64-bit PB Data Bus Byte Lane Definitions
Byte Address
Processor Bus Byte Lanes
PB_A[29:31]
Lane Number
PowerSpan II Pins
PowerQUICC II
Pins
PowerPC 7xx
Pins
000
0
PB_D[0:7]
D[0:7]
DH[0:7]
001
1
PB_D[8:15]
D[8:15]
DH[8:15]
010
2
PB_D[16:23]
D[16:23]
DH[16:23]
011
3
PB_D[24:31]
D[24:31]
DH[24:31]
100
4
PB_D[32:39]
D[32:39]
DL[0:7]
101
5
PB_D[40:47]
D[40:47]
DL[8:15]
110
6
PB_D[48:55]
D[48:55]
DL[16:23]
111
7
PB_D[56:63]
D[56:63]
DL[24:31]
Table 46: PCI Byte Lane Definitions
Byte Address
PCI Byte Lanes