Chapter 7: C790 Bus/G-Bus Bridge
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
7-3
7.4 Endianness
The C790 Bus and G-Bus support both Little and Big Endian byte ordering, while the PCI
Bus only supports fixed Little Endian byte ordering. When the C790 bus is configured for the
Big Endian mode via the Endianness signal, the G-Bus is configured for Big Endian as well.
Bus narrowing is performed by the G-Bridge. As a result of dynamic bus signing, the G-Bus
retries the transaction to locate data in the proper word lane.
Figure 7-3 Bi-Endian Support
Note that all internal registers except those for the SDRAMC are located on the G-Bus.
See Chapter 4 “Address Maps” for more information.
Little Endian
Big Endian
F E D C B A 9 8 7 6 5 4 3 2 1 0
0 1 2 3 4 5 6 7 8 9 A B C D E F
7 6 5 4 3 2 1 0
F E D C B A 9 8
3 2 1 0
7 6 5 4
B A 9 8
F E D C
127
0
127
0
0 1 2 3 4 5 6 7
8 9 A B C D E F
63
0
63
0
63
0
0 1 2 3
4 5 6 7
8 9 A B
C D E F
63
0
C790 Bus
GBus64
shift64
retry & shift32
shift64
retry & shift96
A3 A2 A1 A0
0
× × ×
1
× × ×
A3 A2 A1 A0
0 0
× ×
0 1
× ×
1 0
× ×
1 1
× ×
retry or shift96
shift64
retry or shift32
shift64
GBus32
A3 A2 A1 A0
0
× × ×
1
× × ×
A3 A2 A1 A0
0 0
× ×
0 1
× ×
1 0
× ×
1 1
× ×
Summary of Contents for TMPR7901
Page 1: ...TX System RISC TX79 Family TMPR7901 Symmetric 2 way superscalar 64 bit CPU ...
Page 14: ...Handling Precautions ...
Page 15: ......
Page 17: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 41: ...4 Precautions and Usage Considerations 4 2 ...
Page 42: ...TX7901 User s Manual Rev 6 30T November 2001 DOCUMENT NUMBER M 99 00004 07 ...
Page 43: ......
Page 259: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 1 13 Removed ...
Page 260: ...Chapter 13 Removed TX7901 User s Manual Rev 6 30T Nov 2001 13 2 ...