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Chapter 5: IP Core Architecture
5–3
Key Interfaces
June 2012
Altera Corporation
Stratix V Hard IP for PCI Express
Key Interfaces
If you select the Stratix V Hard IP for PCI Express, your design includes an Avalon-ST
interface to the Application Layer. If you select the Avalon-MM Stratix V Hard IP for
PCI Express, your design includes an Avalon-MM interface to the Application Layer.
The following sections introduce the functionality of all the interfaces shown in
.
.
Avalon-ST Interface
An Avalon-ST interface connects the Application Layer and the Transaction Layer.
This is a point-to-point, streaming interface designed for high throughput
applications. The Avalon-ST interface includes the RX and TX datapaths.
f
For more information about the Avalon-ST interface, including timing diagrams, refer
to the
Avalon Interface Specifications
.
RX Datapath
The RX datapath transports data from the Transaction Layer to the Application
Layer’s Avalon-ST interface. Masking of non-posted requests is partially supported.
Refer to the description of the
rx_st_mask
signal for further information about
masking. For more detailed information about the RX datapath, refer to
TX Datapath
The TX datapath transports data from the Application Layer's Avalon-ST interface to
the Transaction Layer. The Hard IP provides credit information to the Application
Layer for posted headers, posted data, non-posted headers, non-posted data,
completion headers and completion data.
The Application Layer may track credits consumed and use the credit limit
information to calculate the number of credits available. However, to enforce the PCI
Express Flow Control (FC) protocol, the Hard IP also checks the available credits
before sending a request to the link, and if the Application Layer violates the available
credits for a TLP it transmits, the Hard IP blocks that TLP and all future TLPs until
Figure 5–2. Key Interfaces in the Stratix V Hard IP for PCI Express
PMA
PCS
S
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ix V Ha
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PCI Exp
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S
tr
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Avalon-ST
Interrupts
Hard IP Reconfiguration
Clocks and Reset
LMI
Serial Interface
PIPE Interface
Transceiver
Reconfiguration
PHY IP Co
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e fo
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PCI Exp
r
ess (PIPE)