自动测试设备的预算-Automatic Test Equip

文章摘要：This modular approach to software design facilitates its initial development as well as future software changes, especially if the person creating the changes won't be the initial developer. After the tester was completed, a manager requested that it support the testing of an additional IC. The

自动测试设备的预算-Automatic Test Equip,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com

This modular approach to software design facilitates its initial development as well as future software changes, especially if the person creating the changes won't be the initial developer. After the tester was completed, a manager requested that it support the testing of an additional IC. The designer of the tester was able to support the new device in a matter of weeks, as he had organized the software into independent device drivers. Changes to one part of the software did not change other unrelated parts, because the designer aggressively partitioned the code, always anticipating future changes.

When debugging the software you have developed, you will find the RS-232 port is a handy diagnostic tool. In addition to its possible usefulness at the beginning of software development (as described above), you may also find it indispensable at the final phase of the project, while debugging the software. Even if the final design of the tester doesn't provide customer access to the RS-232 port, it can still function as an effective and inexpensive portal for status messages useful to a field technician.

When writing your software, reserve one memory location as a diagnostic enable and another as a diagnostic status indicator. Keep these memory locations in the final version of the software; should a customer encounter a problem, these diagnostic tools can provide valuable information.

A watchdog timer is a useful device, resetting the microprocessor if it gets stuck in an infinite loop. Software must service the watchdog timer at regular intervals to prevent its timer from expiring. When the watchdog timer expires, indicating that the microprocessor is stuck in an infinite loop, it resets the instrument's microprocessor, restoring it to a known operating state. The watchdog-timer reset can initiate the printing of the diagnostic status indicator contents, revealing which part of the software may be responsible for the crash.

Only the input, output, and delay subroutines need to service the watchdog, preventing its timer from expiring. As a general rule, the software spends most of its time in its input or output subroutines, so these subroutines are the best place to service the watchdog timer.

Perhaps this is obvious, but it is still worth saying: Make backup copies of the source code often. Each time you program a new ROM image, copy only the changed files to save time. Also, make sure you have a method for patching ROM code. Even with a limited amount of memory available for patches, the time saved for each instance you compose, compile, and test code is significant, particularly during marathon development sessions.

Conclusion

A PC's parallel port provides a convenient connection between the PC and small, cost-sensitive applications. It is also a useful tool when prototyping a circuit quickly. An RS-232 serial port is typically employed in the same types of applications as the parallel port, but it often requires that a microprocessor be added. Potential problems accompany both parallel and serial ports, although most are usually minor.

The IEEE-488 bus can conveniently connect the PC to multiple test instruments. For the type of test system discussed here, this bus is the clear choice. Although it increases the price of the test system, the capability it offers for connecting more than one instrument at a time to the PC justifies the extra cost.

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