21150 datasheet(13/164 Pages) INTEL

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21150

Preliminary Datasheet

1.2

Data Path

The data path consists of a primary-to-secondary data path for transactions and data flowing in the

downstream direction and a secondary-to-primary data path for transactions and data flowing in the

upstream direction.

Both data paths have the following queues:

• Posted write queue

• Delayed transaction queue

• Read data queue

To prevent deadlocks and to maintain data coherency, a set of ordering rules is imposed on the

forwarding of posted and delayed transactions across the 21150. The queue structure, along with

the order in which the transactions in the queues are initiated and completed, supports these

ordering requirements. Section 6.0 describes the 21150 ordering rules in detail.

See Section 4.0 for a detailed description of 21150 PCI bus operation.

Figure 4 shows the 21150 data path for the downstream direction, and the following sections

describe the data path queues.

Secondary-to-Primary Data Path

Data path for data received on the secondary interface and

driven on the primary interface. This block is used for write

transactions initiated on the secondary PCI bus and for

returning read data for read transactions initiated on the

primary PCI bus. This block contains logic to store and, for

posted write transactions, to increment the address of the

current transaction. This block also performs bus

command and configuration address format translations

Configuration Registers

Configuration space registers and corresponding control

logic. These registers are accessible from the primary

interface only.

Secondary Bus Arbiter Control

Logic for secondary bus arbitration. This block receives

s_req_l<8:0>, as well as the 21150 secondary bus request,

and drives one of the s_gnt_l<8:0> lines or the 21150

secondary bus grant.

Table 1.

21150 Functional Blocks (Sheet 2 of 2)

Figure 4. 21150 Downstream Data Path

LJ-04634.AI4

s_ad

Delayed

Transaction

Queue

Address

Control

Delayed Read Data Queue

Posted Write Data Queue

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