As speeds continue to increase, engineers have been reminded that all signals actually are analog. It's just a convenient abstraction to treat some signals as having only two states. When digital data exhibits obvious analog characteristics, either by degradation or intentionally, Arbs become appropriate generators. Especially for compliance testing that specifies certain types and amounts of serial data impairments for receiver testing, a very high-speed Arb can simplify signal generation. Nevertheless, for parallel data applications, many digital word/timing generators are available with good performance up to a few hundred megahertz. A much smaller number of instruments operate into the gigahertz region. These kinds of products can simulate parts of a system that haven't yet been developed. They provide corner test cases: data values that a system or ASIC might never encounter but still must respond to in a defined way. In an automotive example, spark-plug firing and fuel-injector drive signals can be simulated during engine development. Todd Stocker, marketing manager at Keithley Instruments, commented, "Historically, the first generation of pulse/pattern instruments was designed to facilitate telecomms device testing. In the second phase, designers turned their attention to PC backplane data communications such as the parallel PCI bus. More recently, the emphasis has been on embedded serial buses." The need for parallel-output digital pattern generators hasn't gone away. They're simply being used for different purposes.
展开▼
