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1. Introduction
2. Quick Start Guide
3. Interface Overview
4. Parameters
5. Designing with the IP Core
6. Block Descriptions
7. Registers
8. Programming Model for the DMA Descriptor Controller
9. Programming Model for the Avalon® -MM Root Port
10. Avalon-MM Testbench and Design Example
11. Troubleshooting and Observing the Link
A. PCI Express Core Architecture
B. Root Port Enumeration
C. Document Revision History
2.1. Design Components
2.2. Hardware and Software Requirements
2.3. Directory Structure
2.4. Generating the Design Example
2.5. Simulating the Design Example
2.6. Compiling the Design Example and Programming the Device
2.7. Installing the Linux Kernel Driver
2.8. Running the Design Example Application
7.1.1. Register Access Definitions
7.1.2. PCI Configuration Header Registers
7.1.3. PCI Express Capability Structures
7.1.4. Intel Defined VSEC Capability Header
7.1.5. Uncorrectable Internal Error Status Register
7.1.6. Uncorrectable Internal Error Mask Register
7.1.7. Correctable Internal Error Status Register
7.1.8. Correctable Internal Error Mask Register
7.2.1.1. Avalon-MM to PCI Express Interrupt Status Registers
7.2.1.2. Avalon-MM to PCI Express Interrupt Enable Registers
7.2.1.3. Address Mapping for High-Performance Avalon-MM 32-Bit Slave Modules
7.2.1.4. PCI Express to Avalon-MM Interrupt Status and Enable Registers for Endpoints
7.2.1.5. PCI Express Configuration Information Registers
10.5.1. ebfm_barwr Procedure
10.5.2. ebfm_barwr_imm Procedure
10.5.3. ebfm_barrd_wait Procedure
10.5.4. ebfm_barrd_nowt Procedure
10.5.5. ebfm_cfgwr_imm_wait Procedure
10.5.6. ebfm_cfgwr_imm_nowt Procedure
10.5.7. ebfm_cfgrd_wait Procedure
10.5.8. ebfm_cfgrd_nowt Procedure
10.5.9. BFM Configuration Procedures
10.5.10. BFM Shared Memory Access Procedures
10.5.11. BFM Log and Message Procedures
10.5.12. Verilog HDL Formatting Functions
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A.2. Data Link Layer
The Data Link Layer is located between the Transaction Layer and the Physical Layer. It maintains packet integrity and communicates (by DLL packet transmission) at the PCI Express link level.
The DLL implements the following functions:
- Link management through the reception and transmission of DLL Packets (DLLP), which are used for the following functions:
- Power management of DLLP reception and transmission
- To transmit and receive ACK/NAK packets
- Data integrity through generation and checking of CRCs for TLPs and DLLPs
- TLP retransmission in case of NAK DLLP reception or replay timeout, using the retry (replay) buffer
- Management of the retry buffer
- Link retraining requests in case of error through the Link Training and Status State Machine (LTSSM) of the Physical Layer
Figure 81. Data Link Layer
The DLL has the following sub-blocks:
- Data Link Control and Management State Machine—This state machine connects to both the Physical Layer’s LTSSM state machine and the Transaction Layer. It initializes the link and flow control credits and reports status to the Transaction Layer.
- Power Management—This function handles the handshake to enter low power mode. Such a transition is based on register values in the Configuration Space and received Power Management (PM) DLLPs. All of the Intel® Stratix® 10 Hard IP for PCIe IP core variants do not support low power modes.
- Data Link Layer Packet Generator and Checker—This block is associated with the DLLP’s 16-bit CRC and maintains the integrity of transmitted packets.
- Transaction Layer Packet Generator—This block generates transmit packets, including a sequence number and a 32-bit Link CRC (LCRC). The packets are also sent to the retry buffer for internal storage. In retry mode, the TLP generator receives the packets from the retry buffer and generates the CRC for the transmit packet.
- Retry Buffer—The retry buffer stores TLPs and retransmits all unacknowledged packets in the case of NAK DLLP reception. In case of ACK DLLP reception, the retry buffer discards all acknowledged packets.
- ACK/NAK Packets—The ACK/NAK block handles ACK/NAK DLLPs and generates the sequence number of transmitted packets.
- Transaction Layer Packet Checker—This block checks the integrity of the received TLP and generates a request for transmission of an ACK/NAK DLLP.
- TX Arbitration—This block arbitrates transactions, prioritizing in the following order:
- Initialize FC Data Link Layer packet
- ACK/NAK DLLP (high priority)
- Update FC DLLP (high priority)
- PM DLLP
- Retry buffer TLP
- TLP
- Update FC DLLP (low priority)
- ACK/NAK FC DLLP (low priority)