AXI Multichannel DMA Intel® FPGA IP for PCI Express* User Guide

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ID 817911
Date 4/07/2025
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Document Table of Contents
Document Table of Contents x
1. About This Document 2. Introduction 3. Functional Description 4. Parameters 5. Interfaces 6. Designing with the IP Core 7. Known Issues 8. Revision History for the AXI Multichannel DMA Intel® FPGA IP for PCI Express* User Guide
1. About This Document x
1.1. Intended Audience 1.2. Conventions 1.3. Terms and Acronyms 1.4. Related Information
2. Introduction x
2.1. Overview 2.2. IP Features 2.3. Device Family Support 2.4. IP and Design Example Support 2.5. Recommended Speed Grade 2.6. Resource Utilization 2.7. Release Information
2.2. IP Features x
2.2.1. Root Port Mode Features 2.2.2. Endpoint Mode Features 2.2.3. Design Example Support
4. Parameters x
4.1. IP Settings 4.2. Design Examples
4.1. IP Settings x
4.1.1. PCIe Settings
4.1.1. PCIe Settings x
4.1.1.1. MCDMA Settings 4.1.1.2. PCI Express / PCI Capabilities 4.1.1.3. Base Address Registers
4.1.1.1. MCDMA Settings x
4.1.1.1.1. Multichannel DMA Mode 4.1.1.1.2. Bursting Master Mode 4.1.1.1.3. Bursting Slave Mode 4.1.1.1.4. BAM+BAS Mode 4.1.1.1.5. BAM+MCDMA Mode 4.1.1.1.6. BAM+BAS+MCDMA Mode
4.1.1.2. PCI Express / PCI Capabilities x
4.1.1.2.1. PCIe Device 4.1.1.2.2. PCIe MSI-X
4.1.1.2.2. PCIe MSI-X x
4.1.1.2.2.1. PCIe PF MSI-X 4.1.1.2.2.2. PCIe VF MSI-X
4.2. Design Examples x
4.2.1. Aligning AXI MCDMA IP Settings with AXI Streaming IP for PCI Express
5. Interfaces x
5.1. System Block Diagram 5.2. Clocks and Resets 5.3. PCIe IP-facing Interfaces 5.4. User-facing Interfaces
5.3. PCIe IP-facing Interfaces x
5.3.1. PCIe AXI-ST TX Interface (ss_tx_st) 5.3.2. PCIe AXI-ST RX Interface (ss_rx_st) 5.3.3. Control and Status Register Interface (ss_csr_lite) 5.3.4. Flow Control Credit Interface 5.3.5. Configuration Intercept Interface (CII) 5.3.6. Completion Timeout Interface (ss_cplto) 5.3.7. Function Level Reset Interface 5.3.8. Control Shadow Interface (ss_ctrlshadow)
5.3.4. Flow Control Credit Interface x
5.3.4.1. Transmit Flow Credit Interface (ss_txcrdt) 5.3.4.2. Receive Flow Control Credit Interface (ss_rxcrdt)
5.3.5. Configuration Intercept Interface (CII) x
5.3.5.1. Configuration Intercept Request Interface (ss_cii_req) 5.3.5.2. Configuration Intercept Response Interface (ss_cii_resp)
5.3.7. Function Level Reset Interface x
5.3.7.1. FLR Received Interface (ss_flrrcvd) 5.3.7.2. FLR Completion Interface (ss_flrcmpl)
5.4. User-facing Interfaces x
5.4.1. H2D AXI-ST Source (h2d_st_initatr) 5.4.2. D2H AXI-ST Sink (d2h_st_respndr) 5.4.3. H2D/D2H AXI-MM Master 5.4.4. BAM AXI-MM Master (bam_mm_initatr) 5.4.5. BAS AXI-MM Slave (bas_mm_respndr) 5.4.6. PIO AXI-Lite Master (pio_lite_initiatr) 5.4.7. HIP Reconfig AXI-Lite Slave (user_csr_lite) 5.4.8. User Event MSI-X (user_msix) 5.4.9. User Event MSI (user_msi) 5.4.10. User Function Level Reset (user_flr) 5.4.11. User Configuration Intercept Interface - EP Only 5.4.12. Configuration Slave (cs_lite_respndr) - RP Only
5.4.3. H2D/D2H AXI-MM Master x
5.4.3.1. AXI-MM Write (H2D) 5.4.3.2. AXI-MM Read Channel (D2H)
5.4.11. User Configuration Intercept Interface - EP Only x
5.4.11.1. User Configuration Intercept Request Interface (user_cii_req) 5.4.11.2. User Configuration Intercept Response Interface (user_cii_resp)
6. Designing with the IP Core x
6.1. Generating the IP Core 6.2. IP Core Generation Output 6.3. Simulating the IP Core 6.4. Quick Start Guide
6.4. Quick Start Guide x
6.4.1. Functional Description 6.4.2. Generating the Design Example 6.4.3. Simulating the Design Example 6.4.4. Testing the Design Example
1. About This Document
2. Introduction
3. Functional Description
4. Parameters
5. Interfaces
6. Designing with the IP Core
7. Known Issues
8. Revision History for the AXI Multichannel DMA Intel® FPGA IP for PCI Express* User Guide

5.3.4.1. Transmit Flow Credit Interface (ss_txcrdt)

Before a TLP can be transmitted, flow control logic verifies that the link partner's RX port has sufficient buffer space to accept it. The TX Flow Control interface reports the link partner's available RX buffer space to the MCDMA IP. It reports the space available in units called Flow Control credits for Posted (P), Non-Posted (NP) and Completion (CPL) TLPs (as defined in the RX Flow Control Interface section).

Flow control credits are available for the following TLP categories:
  • Posted transactions: TLPs that do not require a response.
  • Non-Posted transactions: TLPs that require a completion.
  • Completions: TLPs that respond to non-posted transactions.

Interface clock: axi_st_clk

Table 34.  Transmit Flow Credit Interface
Signal Name Direction Description
ss_app_st_txcrdt_tvalid Input

Indicates that the credit information on tdata is valid.
ss_app_st_txcrdt_tdata[18:0] Input

Carries the credit limit information and type of credit.

[15:0]: Credit Limit Value
  • All zero indicates infinite credit for P, NP, CPL
[18:16] : Credit Type
  • 3'b000 - Posted Header Credit
  • 3'b001 - Non-Posted Header Credit
  • 3'b010 - Completion Header Credit
  • 3'b011 - Reserved
  • 3'b100 - Posted Data Credit
  • 3'b101 - Non-Posted Data Credit
  • 3'b110 - Completion Data Credit
  • 3'b111 - Reserved
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