Initiator Access (G-Bus → Pci Bus Address Conversion) - Toshiba TMPR4925 Manual

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Special Cycle
This command issues specially cycles as the initiator only when in the Host mode. This
command issues special cycles on the PCI Bus when writing to the G2P Special Cycle Data
Register (G2PSPC). The written value is output as the special cycle data.
The TX4925 does not support special cycles as the target.
Initiator Access (G-Bus → PCI Bus address conversion)
10.3.4
During PCI initiator access, the G-Bus address of the Burst transaction issued by the G-Bus that was
converted into the PCI Bus address is used to issue a Burst transaction on the PCI Bus. 32-bit physical
address (G-Bus addresses) are used on the G-Bus. Also, 32-bit PCI Bus addresses are used on the PCI
Bus.
Three memory access windows and one I/O access window can be set in the G-Bus space (Figure
10.3.3). The size of each window is variable from 256 bytes to 512 Mbytes. When Burst transactions
are issued to these access windows on the G-Bus, then that G-Bus address is converted into a PCI Bus
address that is used to issue a Burst transaction to the PCI Bus as the initiator. PCI memory access is
issued when the access window is the memory access window. PCI I/O access is issued when the access
window is the I/O access window.
0xFFFF_FFFF
0x0000_0000
0xFFFF_FFFF
0x0000_0000
PCI I/O Space
Memory Access Window
I/O Access Window
Figure 10.3.3 Initiator Access Memory Window
10-8
Chapter 10 PCI Controller
0xFFFF_FFFF
0x00_0000_0000
G-Bus Space
PCI Memory Space