10. Avalon-MM Testbench and Design Example
This chapter introduces the Endpoint design example including a testbench, BFM, and a test driver module. You can create this design example using design flows described in Quick Start Guide. This testbench uses the parameters that you specify in the Quick Start Guide.
This testbench simulates up to x16 variants. However, the provided BFM only supports x1 - x8 links. It supports x16 variants by downtraining to x8. To simulate all lanes of a x16 variant, you can create a simulation model to use in an Avery testbench. This option is currently available for the Avalon® -ST variants only. For more information refer to AN-811: Using the Avery BFM for PCI Express Gen3x16 Simulation on Intel Stratix 10 Devices.
When configured as an Endpoint variation, the testbench instantiates a design example and a Root Port BFM, which provides the following functions:
- A configuration routine that sets up all the basic configuration registers in the Endpoint. This configuration allows the Endpoint application to be the target and initiator of PCI Express transactions.
- A Verilog HDL procedure interface to initiate PCI Express transactions to the Endpoint.
This testbench simulates a single Endpoint DUT.
The testbench uses a test driver module, altpcietb_bfm_rp_gen3_x8.sv, to exercise the target memory and DMA channel in the Endpoint BFM. The test driver module displays information from the Root Port Configuration Space registers, so that you can correlate to the parameters you specify using the parameter editor. The Endpoint model consists of an Endpoint variation combined with the DMA application.
Starting from the Intel® Quartus® Prime 18.0 release, you can generate an Intel® Arria® 10 PCIe example design that configures the IP as a Root Port. In this scenario, the testbench instantiates an Endpoint BFM and a JTAG master bridge.
The simulation uses the JTAG master BFM to initiate CRA read and write transactions to perform bus enumeration and configure the endpoint. The simulation also uses the JTAG master BFM to drive the TXS Avalon® -MM interface to execute memory read and write transactions.
Your Application Layer design may need to handle at least the following scenarios that are not possible to create with the Intel testbench and the Root Port BFM:
- It is unable to generate or receive Vendor Defined Messages. Some systems generate Vendor Defined Messages and the Application Layer must be designed to process them. The Hard IP block passes these messages on to the Application Layer which, in most cases should ignore them.
- It can only handle received read requests that are less than or equal to the currently set equal to Device > PCI Express > PCI Capabilities > Maximum payload size using the parameter editor. Many systems are capable of handling larger read requests that are then returned in multiple completions.
- It always returns a single completion for every read request. Some systems split completions on every 64-byte address boundary.
- It always returns completions in the same order the read requests were issued. Some systems generate the completions out-of-order.
- It is unable to generate zero-length read requests that some systems generate as flush requests following some write transactions. The Application Layer must be capable of generating the completions to the zero length read requests.
- It uses a fixed credit allocation.
- It does not support parity.
- It does not support multi-function designs which are available when using Configuration Space Bypass mode or Single Root I/O Virtualization (SR-IOV).
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