Various Types of Transaction-Based Interfaces (TLM) for DisplayPort VIP

Introduction

Different RTL designs often require different specially designed parallel interfaces. These different interface requirements serve varying needs, such as certain blocks not being ready when the design is under development. To speed up simulation during unit testing, DisplayPort needs to connect to other protocols. Instead of creating a new physical pin interface, this blog introduces a Transaction-Based Customer Interface, which is compatible with all users' specific parallel interface requirements. The traditional way of creating a new physical pin interface is time-consuming. Even a slight difference in the interface definition requires the development of a full pin interface as the pin interface is 1 to 1 solution. Also, multiple physical interfaces are confusing to the user. This interface allows users to use the VIP transactions and callback instead of predefined physical pins. For example, customers request a 32-bit aligned interface and CIO mode interface. With traditional methods, VIP needs to create two different parallel interfaces. With the transaction-based customer interface, VIP only uses one interface to fulfill two different customer requirements.

Solution

To address the above issue, we are proposing the Transaction-Based Customized Interface is a configurable interface compatible with all user's specific parallel interface requirements. This interface allows users to use the VIP transactions and callback instead of predefined physical pins. Instead of using the signals on physical pins, the DisplayPort VIP provides callbacks and transactions. Users can use callbacks and transactions to access the data and modify a transaction inside of VIP. This provides flexibility to the user.

Below is the test topology of Source VIP connecting to Sink DUT without the pin interface. Figure 1 shows the flow with Source as VIP and Sink as DUT. In this scenario, Source VIP provides data in the form of predefined field transactions through callback. The predefined fields data masks or bundles to form a customer-defined pin interface in the testbench. Special sideband signals are also extracted from transaction fields. DUT detects the data and control signals through the defined pin interface.

Figure 1: Source VIP connects to Sink DUT with the Transaction-Based Customized Interface

Example

Interface#1 – 32-bit Parallel Interface

In 128b/132b channel coding, the customer requested a 32-bit parallel interface instead of transmitting/receiving 1 bit at a time in order to fasten simulation time without a serialization block. From the spec, each block has 132bit (FEC disabled) or 129bit (FEC enabled). This nature block is not aligned with the 32-bit requirement. Blocks need to break to 32 bits. Traditionally, VIP must create a new physical interface, serialize the block first, and reform it to align as 32-bit symbols. In the proposed way, VIP provides the transaction, and TB aligns it to a 32-bit symbol, and there is no need to create a physical interface. Below is the figure to illustrate that VIP is able to provide 32-bit data from a transaction-based interface.

Figure 2: Customized 32bits parallel interface

Interface#2

Another interface is designed with a Transaction-Based interface. The testbench is able to extract from transactions and fields to generate data and control signals as they request.

Figure 3: Customized CIO interface

Conclusion

The DisplayPort VIP Transaction-Based interface supports both 128b/132b channel coding and 8b/10b channel coding, with different features, such as ALPM (Advanced Link Power Management) and FEC (Forward Error Correction). User can verify their RTL designs with different interfaces using a Transaction-Based interface. In 128b/132b channel coding, the user can configure a symbol-based 32-bit interface, or super symbol-based 132-bit, etc. In 8b/10b channel coding, the user can configure to include or not include skew, FEC, etc. Users can also configure it to switch between the 8b/10b channel and the 128b/132bit channel.

This Transaction-Based customer interface can support all customers' specific parallel interfaces. It is compatible with all customers' specific parallel interfaces to fasten the integration and simulation time.

More Information

Cadence has a very mature Verification IP solution. Verification over many different configurations can be used with DisplayPort 2.1 and DisplayPort 1.4 designs, so you can choose the best version for your specific needs. The DisplayPort VIP provides a full-stack solution for Sink and Source devices with a comprehensive coverage model, protocol checkers, and an extensive test suite.

More details are available on the DisplayPort Verification IP product page and Simulation VIP pages. If you have any queries, feel free to contact us at talk_to_vip_expert@cadence.com.