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Processor emulation technology
 Q: To start off, Larry, could you briefly explain what processor emulation is?
A: Sure, it’s really a powerful concept that came out of a very real need in the board bring-up and debug areas. Later, it migrated into functional test. Staging a hot mock-up system to do functional test can be very labor-intense and the diagnostics when you uncover a failure are not very good at all. By taking control of an on-board device, such as a processor, emulation can control the circuit board and assert routines and patterns throughout the board, like read/write actions to memory and I/O. This avoids some of the access problems densely populated boards have. Emulation can even perform ROM boot code tests which verify that the contents of ROM matches a predefined load. In addition, emulation can substitute diagnostic code for the system’s normal boot code.
Q: What are some of the advantages of processor emulation testing?
A: Emulation test bypasses the system’s or the board’s usual operating system, so the time to run a particular test can be reduced from minutes to seconds. This can reduce the overall test time for a board significantly. And comprehensive diagnostic information can be generated all the way down to an individual component. Another very useful bit of functionality is the fact that emulation test can be done on dead boards, which often can’t be diagnosed by any other test method.
Q: How are the tests applied so quickly?
A: As I said, you avoid the operating system with processor emulation test and the emulation tests, such as those that our MicroMaster system applies, are executed at CPU speeds, since the CPU is applying them. That means that debug and test patterns can be run at full processor speeds and you don’t have the operating system or other software getting in the way.
Q: You mentioned that doing functional test with a hot mock-up of the system-under-test can be very labor-intense. How about for processor emulation testing?
A: Setup time is kept to a minimum because we provide preprogrammed device libraries and an automatic test generation (ATG) engine with MicroMaster. The ATG engine interrogates or scans a known-good-board to identify the devices that are present and then test scripts are automatically created for application on subsequent boards in manufacturing or a repair operation.
Q: How about programming on-board devices like flash memory or complex programmable logic devices (CPLD)?
A: Yes, processor emulation can used to program devices that are already soldered on the board and which can be reached by the processor. This is an important functionality for some users, but it’s just part of what processor emulation can do. Some users I’ve talked to seem to be under the impression that in-system programming is the only thing that processor emulation can do and that’s simply not the case.
Q: How would someone incorporate processor emulation testing in a test strategy?
A: It’s really pretty simple. Because MicroMaster runs on a PC, just like ScanWorks, it’s very easy to integrate both processor emulation and boundary-scan test into an overall test strategy or plan for a design. In fact, both MicroMaster and ScanWorks can utilize the same controller card in the PC. And they are both compatible with the popular test executives so connection to the wider enterprise is straightforward.
To read an article that appeared in Evaluation Engineering Magazine
on processor emulation, click here.
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