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15. Testbench and Design Example
This chapter introduces the Root Port or Endpoint design example including a testbench, BFM, and a test driver module. You can create this design example for using design flows described in Getting Started with the Arria V Hard IP for PCI Express .
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.
When configured as a Root Port, the testbench instantiates a Root Port design example and an Endpoint model, which provides the following functions:
- A configuration routine that sets up all the basic configuration registers in the Root Port and the Endpoint BFM. 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 BFM.
This testbench simulates a single Endpoint or Root Port DUT.
The testbench uses a test driver module, altpcietb_bfm_rp_<gen>_x8.sv, to exercise the target memory. At startup, the test driver module displays information from the Root Port Configuration Space registers, so that you can correlate to the parameters you specified using the parameter editor.
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. Consequently, you must design the Application Layer 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 Maximum payload size option specified under PCI Express/PCI Capabilities heading under the Device tab 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 fixed credit allocation.
- It does not support parity.
- It does not support multi-function designs.
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