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Overview
NI Multisim is an intuitive schematic capture and SPICE simulation package that makes the design and exploration of analog, mixed-mode, and even microcontroller circuits easy for both professionals and academics.
Multisim has become a tool of choice in many undergraduate engineering programs and institutions across the world, because Multisim has been designed with the needs of the educator in mind. In this article we will investigate Single Symbol Digital Components help to bridge the gap between theory and reality. For a description of all the features of Multisim, and how they can relate to academia, see the Multisim Educational features article.
What is a Single Symbol Digital Component?
Single Symbol Digital Components are parts available in Multisim 10 that use exactly one graphic element to represent an entire integrated circuit such as a 74LS00D. The single symbol matches the pinout of the chip as specified by the datasheet. For example the images below are the single symbol representation and the datasheet pinout of the 74LS00D, which is a quadruple 2-input NAND gate circuit.
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Figure 1 – 74LS00D Single Symbol Digital Representation |
Figure 2 – 74LS00D Datasheet Pinout (Datasheet from Motorola) |
Figure 3 - 74LS00N Picutre (souce) |
The Benefit of Single Symbol Digital Components
Single symbol digital components are useful because they have power, ground, and other connections visible that must be wired in the lab. Students will see as soon as they place a NAND gate how it must be wired in the real-world. By using single symbol components, students will save valuable lab time by developing an appreciation for how components must be connected in the real world.
For example, if a student is to use a NAND gate in their design, they might need to use the 74LS00D integrated circuit once they are in the lab. The 74LS00D chip looks nothing like the standard symbols used to represent the logic functions in textbooks and other resources. Students can spend waste a significant amount of time while trying to understand power, ground, and the overall pinout of the chip.
Standard logic symbols differ from single symbol components because standard logic symbols are implementation-independent; they make no indication of the technology used to carry-out the function described by the symbol. For example in the figure below the 2-input AND gate could be implemented in one of several technologies such as traditional TTL, CMOS, or even as part of an FPGA design.
Figure 3 -Selected Standard Logic Symbols
Because of the independence of standard symbols from implementation, students can often find the transition from theoretical work to laboratory prototyping difficult. Given that a significant amount of laboratory work is still carried out on breadboards or breadboard prototyping workstations like the NI ELVIS, it is important for students to understand at least some of the specifics of implementation. This understanding is ideally achieved using single symbol digital components.
Related Links
Virtual Prototyping using NI Multisim
Microcontroller Unit Co-Simulation For SPICE-Based Circuits
NI Circuit Design Technical Library
Electronics Education Courseware
Comparison between the Student and Full Educational version of NI Multisim
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