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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. Document Revision History
A. PCI Express Core Architecture
B. Root Port Enumeration
C. Troubleshooting and Observing the Link Status
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.1. Transaction Layer
The Transaction Layer is located between the Application Layer and the Data Link Layer. It generates and receives Transaction Layer Packets. The following illustrates the Transaction Layer. The Transaction Layer includes three sub-blocks: the TX datapath, Configuration Space, and RX datapath.
Tracing a transaction through the RX datapath includes the following steps:
- The Transaction Layer receives a TLP from the Data Link Layer.
- The Configuration Space determines whether the TLP is well formed and directs the packet based on traffic class (TC).
- TLPs are stored in a specific part of the RX buffer depending on the type of transaction (posted, non-posted, and completion).
- The receive reordering block reorders the queue of TLPs as needed, fetches the address of the highest priority TLP from the TLP FIFO block, and initiates the transfer of the TLP to the Application Layer.
Tracing a transaction through the TX datapath involves the following steps:
- The Transaction Layer informs the Application Layer that sufficient flow control credits exist for a particular type of transaction using the TX credit signals. The Application Layer may choose to ignore this information.
- The Application Layer requests permission to transmit a TLP. The Application Layer must provide the transaction and must be prepared to provide the entire data payload in consecutive cycles.
- The Transaction Layer verifies that sufficient flow control credits exist and acknowledges or postpones the request. If there is insufficient space in the retry buffer, the Transaction Layer does not accept the TLP.
- The Transaction Layer forwards the TLP to the Data Link Layer.
Figure 74. Architecture of the Transaction Layer: Dedicated Receive Buffer