TSI352 Datasheet, PDF (35/183 Pages) Integrated Device Technology – This chapter discusses the following topics about the Tsi352

2. PCI Interface
35
2.3
Configuration Transactions
Configuration transactions are used to initialize a PCI system. Every PCI device has a configuration
space that is accessed by configuration commands. All Tsi352 registers are accessible in configuration
space only.
In addition to accepting configuration transactions for initialization of its own configuration space, the
Tsi352 also forwards configuration transactions for device initialization in hierarchical PCI systems, as
well as for special cycle generation.
To support hierarchical PCI bus systems, two types of configuration transactions are specified: Type 0
and Type 1.
• Type 0 configuration transactions are issued when the intended target resides on the same PCI bus
as the initiator. A Type 0 configuration transaction is identified by the configuration command and
the lowest 2 bits of the address set to 00b.
• Type 1 configuration transactions are issued when the intended target resides on another PCI bus,
or when a special cycle is to be generated on another PCI bus. A Type 1 configuration command is
identified by the configuration command and the lowest 2 address bits set to 01b.
Figure 5 and Figure 6 show the address formats for Type 0 and Type 1 configuration transactions.
Figure 5: Type 0 Configuration Transaction Address Format
31
11
10 8
7
2
1
0
Reserved
Function
number
Register
0
0
number
Figure 6: Type 1 Configuration Transaction Address Format
31
24
Reserved
23
16
Bus number
15
11
Device number
10 8
Function
number
7
2
1
0
Register
0
1
number
The register number is found in both Type 0 and Type 1 formats and gives the Dword address of the
configuration register to be accessed. The function number is also included in both Type 0 and Type 1
formats and indicates which function of a multifunction device is to be accessed. For single function
devices, this value is not decoded. Type 1 configuration transaction addresses also include a 5-bit field
designating the device number that identifies the device on the target PCI bus that is to be accessed. In
addition, the bus number in Type 1 transactions specifies the PCI bus to which the transaction is
targeted.
Integrated Device Technology
www.idt.com
Tsi352 User Manual
80D6000_MA001_03