Experiments with a sixteen-digit seven-segment oscilloscope display

This paper describes experiments performed by students in a second-semester digital design laboratory using an output display device that shows up to sixteen hexadecimal digits in seven-segment format on a standard analog oscilloscope. The display device itself has been described in an earlier ASEE paper¹, and is the latest in a series of display innovations that the author has used in his advanced digital laboratory^2,3. This display relieves students from implementing an output interface for circuits under study, and allows them to concentrate on the core circuit they are designing, whether it be a multiplier, a hardware data structure, or other special-purpose application. This output device, when combined with a similarly-designed keypad input device not described here, provides a universal input/output system that interfaces in a standard way to student digital designs. The display device used here employs an analog oscilloscope screen as the display medium. Analog oscilloscopes are found these days collecting dust in academic electronics labs, as they have generally been replaced with more modern digital instruments. However, these old oscilloscopes still have long lives remaining, and applications such as this make innovative use of their characteristics. This unusual use for a familiar test instrument intrigues students and makes them wonder how a standard oscilloscope can be made to produce such a display. This leads to opportunities to demonstrate to students that "outside-the- box" approaches sometimes result in successful innovation. The course using this display device in its lab is a second course in digital circuit design. The course emphasizes functional units that are often found in digital computers, such as arithmetic circuits (multi-digit adders, multipliers), hardware data structure implementation (stack, queue), and memory circuits. Examples of each of these types of experiments and how they use this oscilloscope display are presented in this paper.