3. Data Path
44
Tsi384 User Manual
May 5, 2014
Integrated Device Technology
www.idt.com
3.6
Short Term Caching
This feature provides performance improvements in situations where upstream devices are not able to
stream data continuously to meet the prefetching needs of the Tsi384. As defined in the
PCI-to-PCI
Bridge Specification (Revision 1.2)
, when the bus master completes a transaction, the bridge is required
to discard the balance of any data that was prefetched for the master. To prevent performance impacts
when dealing with devices between requester and completer that can only stream data of 128 to 512
bytes due to buffering constraints, the Tsi384 uses “Short Term Caching.” This feature applies only
when the PCI/X Interface is operating in PCI mode, and provides a time-limited read data cache in
which the Tsi384 will not discard prefetched read data after the request completes on the initiating bus.
To enable Short Term Caching, set the STC_EN bit in the
“PCI Miscellaneous Control and Status
. When enabled, the Tsi384 does not discard the additional prefetched data when the read
transaction completes on the initiating bus. The Tsi384 then continues to prefetch data up to the amount
specified in the
. If the initiator generates a new transaction that requests
the previously prefetched data, the Tsi384 returns that data.
The Tsi384 discards data after some of the data for a request is returned to the initiator and one of the
following conditions is met:
•
Short-term discard timer is expired before the initiator has requested additional data (see
“Short-term Caching Period Register”
).
•
An upstream posted transaction is received on the PCI/X Interface
3.7
Lane Reversal and Polarity Reversal
The Tsi384 supports lane reversal, lane degradation, and polarity reversal. For information on how to
use these features, see the
Tsi384
Board Design Guidelines
.
Short-term caching should only be used in systems that can ensure the data provided to the
master has not been modified since the initial transaction.
Summary of Contents for TSI384
Page 1: ... IDT Tsi384 PCIe to PCI Bridge User Manual May 5 2014 ...
Page 10: ...Contents 10 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 56: ...4 Addressing 56 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 74: ...6 Bridging 74 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 78: ...7 PCI X Arbitration 78 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 136: ...12 Serial EEPROM 136 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 142: ...13 JTAG 142 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 268: ...16 Packaging 268 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 276: ...276 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...
Page 280: ...Index 280 Tsi384 User Manual May 5 2014 Integrated Device Technology www idt com ...