IDT Tsi310TM, User Manual, Page: 39 / 207

2. Bus Operation 39
Tsi310 User Manual
80B6020_MA001_05
On the secondary bus, the Tsi310 responds to a Type 0 configuration transaction by accepting
the transaction when the following conditions are met during the address phase:
• S_C/BE(3:0)# command indicates a configuration read or configuration write transaction
• S_AD(1:0) are b'00'
• S_IDSEL is asserted
• The Bus Master control bit in the Command Register must be set to b‘1’ from the Primary
Interface
The function number is not decoded since the bridge is a single-function device. All
configuration transactions to the bridge are handled as DWord (single data phase) operations.
2.4.1.1 Type 0 Configuration Transaction Limitation
The Tsi310 has a transaction limitation when its Primary interface is configured in PCI-X mode,
and a Configuration write accesses the Tsi310 register space after it is configured by the host
processor through the Primary interface. The host processor is responsible for configuring all
devices on the Primary bus at power-up, and assigns each device a unique “device number.”
This number is defined by AD[15:11] of the address Type 0 configuration write transaction.
Each time a configuration write is initiated to the Tsi310 this device number is updated. The
device number can be read at offset 0x84 of Tsi310’s configuration space (see
Section 5.5.20 on
page 137 ).
The Tsi310 contains a feature that allows devices connected to its Secondary interface to access
Tsi310’s registers through Type 0 configuration cycles. For example, when a Type 0
configuration write is initiated to the bridge’s Secondary interface the contents of the Tsi310
device number is updated. Users should be aware, however, that transaction accesses to the
Tsi310 from the Secondary interface could overwrite the bridge’s device number. As a result, it
is possible that two devices may have the same device number.
If a user needs to access the Tsi310 from the Secondary interface after reset (for
example, to set up Opaque regions), IDT recommends completing a configuration
read of offset 0x84 to determine the Tsi310's device number assigned upon initial
configuration. Once the device number is determined it must be included in
AD[15:11] of any configuration write access to the bridge from the Primary or
Secondary interface.