Chapter 8: PCI/G-Bus Bridge
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
8-26
8.3.2.3
PCI to G-Bus Memory Windows
The PCI accesses G-Bus locations through PCI memory windows called p2gwindows. Each
p2gwindow is defined by the normal PCI base register mechanism. The PGB provides four
PCI base registers; three DAC memory base pairs, and a single I/O base. These PCI base
registers allow for four individual p2gwindows. An additional register called p2gBase
provides the base address of the G-Bus transaction performed.
8.3.2.3.1 p2g Base Address Registers (p2gBase)
When a G-Bus cycle is initiated, p2gBase is added to the PCI offset address to produce the
effective G-Bus address. G-Bus access to these registers is allowed using the G-Bus single
cycle mode.
The p2g Base Address Register fields are detailed below and in Table 8-13.
63
32
0
32
31
3
2
0
p2gBase [31:3]
0
29
3
Table 8-13 p2gBase Address Register Field Descriptions
Bits
Field
R/W
Description
63:32
–
R/O
Reserved. Read back at “0”. (0)
31:3
p2gBase
R/W
Address used for base of G-Bus transaction. Cleared on reset. (0)
2:0
–
R/O
Reserved. Read back as “0”. (0)
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 ...