TMPR4925 datasheet(270/590 Pages) TOSHIBA

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Chapter 10 PCI Controller

10-8

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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

The TX4925 does not support special cycles as the target.

10.3.4

Initiator Access (G-Bus

→ PCI Bus address conversion)

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.

Figure 10.3.3 Initiator Access Memory Window

0x0000_0000

0xFFFF_FFFF

0x0000_0000

0x00_0000_0000

0xFFFF_FFFF

PCI I/O Space

G-Bus Space

PCI Memory Space

Memory Access Window

I/O Access Window

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