IPR-PCIE/1 Altera, IPR-PCIE/1 Datasheet - Page 53

• Manufacturer Part Number: IPR-PCIE/1
• Description: IP CORE Renewal Of IP-PCIE/1
• Manufacturer: Altera
• Type: MegaCorer

Specifications of IPR-PCIE/1

• Software Application: IP CORE, Interface And Protocols, PCI
• Supported Families: Arria GX, Cyclone II, HardCopy II, Stratix II
• Core Architecture: FPGA
• Core Sub-architecture: Arria, Cyclone, Stratix
• Rohs Compliant: NA
• Function: PCI Express Compiler, x1 Link Width
• License: Renewal License
• Lead Free Status / RoHS Status: na
• Lead Free Status / RoHS Status: na

Chapter 3: Parameter Settings
Buffer Setup
Table 3–4. Buffer Setup Parameters (Part 2 of 3)
December 2010 Altera Corporation
Maximum retry
packets
Desired
performance for
received requests
Desired
performance for
received
completions
Parameter
4–256
(powers of 2)
Maximum,
High,
Medium, Low
Maximum,
High,
Medium, Low
Value
Set the maximum number of packets that can be stored in the retry buffer. For the
hard IP implementation this parameter is set to 64.
Specifies how to configure the RX buffer size and the flow control credits:
Low—Provides the minimal amount of space for desired traffic. Select this option
when the throughput of the received requests is not critical to the system design.
This setting minimizes the device resource utilization.
Because the Arria II GX and Stratix IV hard IP have a fixed RX Buffer size, the
choices for this parameter are limited to a subset of these values. For Max
payload size of 512 bytes or less, the only available value is Maximum. For Max
payload size of 1 KBytes or 2 KBytes a tradeoff has to be made between how
much space is allocated to requests versus completions. At 1 KByte and 2 KByte
Max payload size, selecting a lower value for this setting forces a higher setting
for the Desired performance for received completions.
Note that the read-only values for header and data credits update as you change
this setting.
For more information, refer to
how the Maximum payload size and Desired performance for received
completions that you choose affect the allocation of flow control credits.
Maximum—Provides additional space to allow for additional external delays (link
side and application side) and still allows full throughput.
If you need more buffer space than this parameter supplies, select a larger
payload size and this setting. The maximum setting increases the buffer size and
slightly increases the number of logic elements (LEs), to support a larger payload
size than is used. This is the default setting for the hard IP implementation.
Medium—Provides a moderate amount of space for received completions. Select
this option when the received completion traffic does not need to use the full link
bandwidth, but is expected to occasionally use short bursts of maximum sized
payload packets.
Low—Provides the minimal amount of space for received completions. Select
this option when the throughput of the received completions is not critical to the
system design. This is used when your application is never expected to initiate
read requests on the PCI Express links. Selecting this option minimizes the device
resource utilization.
For the hard IP implementation, this parameter is not directly adjustable. The
value set is derived from the values of Max payload size and the Desired
performance for received requests parameter.
For more information, refer to
how the Maximum payload size and Desired performance for received
completions that you choose affects the allocation of flow control credits.
Chapter 11, Flow
Chapter 11, Flow
Description
Control. This analysis explains
Control. This analysis explains
PCI Express Compiler User Guide
3–11