Verifying designs that contain custom protocols can be tricky. By their very definition, the protocol does not conform to any standard specification, and therefore the creator of the custom protocol must also be responsible for its verification. This is not the ideal case, but is something that designers must contend with when using a customer protocol in their design.
In this article, we explore a few tips to help insure your custom protocol testing can be as smooth as possible.
- Make sure your custom protocol is defined to the extent that other standard protocols are. Nothing is worse than having to verify your interface using a specification that is fluid. The biggest element that people miss are definition of illegal or error conditions. In other words, "What should the device do if it encounters an abnormal condition, such as signal loss, or extreme delay?" When you are able to define such conditions and design them into your silicon, you will reduce your debug and test time significantly.
- Custom speeds require special test equipment. If your custom protocol is using a speed that is non-standard, check to see that your test equipment, particularly the protocol analyzer, can handle it. For protocol analyzers, understanding the speed at which to capture each bit is fundamental to analysis.
- Verify operation of the protocol before publishing the specification to your team or department. Nothing is worse than having your specification published, only to find later on that it is inadequate for the functions needed. Verification should include hooking up prototype hardware to test equipment that can generate traffic and inject random errors. This way you can check both compliance and error recovery at the same time.
- Use a protocol analyzer where you can modify your specification on the fly. This will save you time and money compared to analyzers that do not have this capability. There are two types of protocol analyzers with regards to support for custom protocols. The first type is where the custom protocol has to be "hard wired" into the analyzer using a user provided specification. The analyzer will then be configured to only handle that particular protocol. Changes to the specification will require that the analyzer be sent back to the manufacturer to adjust.
The second type is an “open database” protocol analyzer, where the user is given access to the database, thereby making it easier to make modifications if necessary. The time and costs savings is obvious. The user can make database modifications without having to send back the unit to the factory.
Absolute Analysis has a full line of serial interface testers that can handle multiple, mixed, and custom protocols all on the same hardware and same user interface. Call us now for a demo 1-805-376-6048.
