1. Functional Overview
28
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
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Figure 4: Concurrent Read Process with PowerSpan II
When Master 2 makes its first read request in Step 2, it is retried but information about the read request
is latched and initiates a read on the other bus. This occurs even though a read is in progress for
Master 1.
PowerSpan II can simultaneously support two reads to the Processor Bus and two reads to the PCI bus.
1.6.1.1
Conventional Reads and Retries
In conventional FIFO-based bridge architectures, bus masters must take turns for read opportunities
and incur multiple retries while waiting.
illustrates the read process for subsequent reads where
retries are incurred while a pending read is completed.
Master 1: Makes a read request
and is retried.
READ 1 Request
READ 1
Read Request
Master 2: Makes an initial read
request and is retried.
READ 2
Master 1: Takes the read data
Master 2: Takes read data
Read Request
Master 1: Makes request
1.
2.
3.
4.