Digital ICs {if 0}- Education

What does it mean, in general terms, to encode something? Conversely, what does it mean to decode something? Perhaps the most common context for these terms to be used is cryptography (code-making and code-breaking), but they also find application in common digital circuits.

Suppose we wanted to build a device that could add two binary bits together. Such a device is known as a half-adder, and its gate circuit looks like this: The Σ symbol represents the “sum” output of the half-adder, the sum’s least significant bit (LSB). Cout represents the “carry” output of the half-adder, the sum’s most significant bit (MSB). If we were to implement this same function in ladder

Up to now, every circuit that was presented was a combinatorial circuit. That means that its output is dependent only by its current inputs. Previous inputs for that type of circuits have no effect on the output. However, there are many applications where there is a need for our circuits to have “memory”; to remember previous inputs and calculate their outputs according to them. A circuit whose output depends not

The purpose of the parallel-in/ parallel-out shift register is to take in parallel data, shift it, then output it as shown below. A universal shift register is a do-everything device in addition to the parallel-in/ parallel-out function. Above we apply four bit of data to a parallel-in/ parallel-out shift register at DA DB DC DD. The mode control, which may be multiple inputs, controls parallel loading vs shifting. The mode

What are Time-Delay Relays? Some relays are constructed with a kind of “shock absorber” mechanism attached to the armature which prevents immediate, full motion when the coil is either energized or de-energized. This addition gives the relay the property of time-delay actuation. Time-delay relays can be constructed to delay armature motion on coil energization, de-energization, or both. Time-delay relay contacts must be specified not only as either normally-open or normally-closed

PARTS AND MATERIALS 4511 BCD-to-7seg latch/decoder/driver (Radio Shack catalog # 900-4437) Common-cathode 7-segment LED display (Radio Shack catalog # 276-075) Eight-position DIP switch (Radio Shack catalog # 275-1301) Four 10 kΩ resistors Seven 470 Ω resistors One 6 volt battery Caution! The 4511 IC is CMOS, and therefore sensitive to static electricity! CROSS-REFERENCES Lessons In Electric Circuits, Volume 4, chapter 9: “Combinational Logic Functions” LEARNING OBJECTIVES How to use the 4511 7-segment decoder/display driver IC Gain familiarity with

If we were to connect two inverter gates together so that the output of one fed into the input of another, the two inversion functions would “cancel” each other out so that there would be no inversion from input to final output: While this may seem like a pointless thing to do, it does have practical application. Remember that gate circuits are signal amplifiers, regardless of what logic function they

What Is a R/2nR DAC Circuit? The R/2nR DAC circuit, otherwise known as the binary-weighted-input DAC, is a variation on the inverting summing op-amp circuit. (Note that “summing” circuits are sometimes also referred to as “summer” circuits.) If you recall, the classic inverting summing circuit is an operational amplifier using negative feedback for controlled gain, with several voltage inputs and one voltage output. The output voltage is the

Don’t just sit there! Build something!! Learning to mathematically analyze circuits requires much study and practice. Typically, students practice by working through lots of sample problems and checking their answers against those provided by the textbook or the instructor. While this is good, there is a much better way. You will learn much more by actually building and analyzing real circuits, letting your test equipment provide the “answers” instead

NAND and NOR gates possess a special property: they are universal. That is, given enough gates, either type of gate is able to mimic the operation of any other gate type. For example, it is possible to build a circuit exhibiting the OR function using three interconnected NAND gates. The ability for a single gate type to be able to mimic any other gate type is one enjoyed only by

Before the advent of solid-state logic circuits, logical control systems were designed and built exclusively around electromechanical relays. Relays are far from obsolete in modern design, but have been replaced in many of their former roles as logic-level control devices, relegated most often to those applications demanding high current and/or high voltage switching. Systems and processes requiring “on/off” control abound in modern commerce and industry, but such control

One caveat with signed binary numbers is that of overflow, where the answer to an addition or subtraction problem exceeds the magnitude which can be represented with the alloted number of bits. Remember that the place of the sign bit is fixed from the beginning of the problem. With the last example problem, we used five binary bits to represent the magnitude of the number, and the left-most (sixth) bit

PARTS AND MATERIALS 4011 quad NAND gate (Radio Shack catalog # 276-2411) 4001 quad NOR gate (Radio Shack catalog # 276-2401) Eight-position DIP switch (Radio Shack catalog # 275-1301) Ten-segment bar graph LED (Radio Shack catalog # 276-081) One 6 volt battery Three 10 kΩ resistors Two 470 Ω resistors Caution! The 4011 IC is CMOS, and therefore sensitive to static electricity! Although the parts list calls for a ten-segment LED unit, the illustration shows two individual LEDs being used instead.

While the binary numeration system is an interesting mathematical abstraction, we haven’t yet seen its practical application to electronics. This chapter is devoted to just that: practically applying the concept of binary bits to circuits. What makes binary numeration so important to the application of digital electronics is the ease in which bits may be represented in physical terms. Because a binary bit can only have one of two

Try out our 555 Timer Astable Circuit in our Tools section. PARTS AND MATERIALS One 9V Battery Battery Clip (Radio Shack catalog # 270-325) Mini Hook Clips (soldered to Battery Clip, Radio Shack catalog # 270-372) U1 - 555 timer IC (Radio Shack catalog # 276-1723) D1 - Red light-emitting diode (Radio Shack catalog # 276-041 or equivalent) D2 - Green light-emitting diode (Radio Shack catalog # 276-022 or equivalent) R1,R2 - 1 KΩ 1/4W Resistors R3

It is sometimes desirable to have a logic gate that provides both inverted and non-inverted outputs. For example, a single-input gate that is both a buffer and an inverter, with a separate output terminal for each function. Or, a two-input gate that provides both the AND and the NAND functions in a single circuit. Such gates do exist and they are referred to as complementary output gates. The general symbology

Larger Karnaugh maps reduce larger logic designs. How large is large enough? That depends on the number of inputs, fan-ins, to the logic circuit under consideration. One of the large programmable logic companies has an answer. Altera’s own data, extracted from its library of customer designs, supports the value of heterogeneity. By examining logic cones, mapping them onto LUT-based nodes and sorting them by the number of inputs that

Up to this point we have considered logic reduction problems where the input conditions were completely specified. That is, a 3-variable truth table or Karnaugh map had 2n = 23 or 8-entries, a full table or map. It is not always necessary to fill in the complete truth table for some real-world problems. We may have a choice to not fill in the complete table. For example, when dealing with BCD (Binary

A demultiplexer, sometimes abbreviated dmux, is a circuit that has one input and more than one output. It is used when a circuit wishes to send a signal to one of many devices. This description sounds similar to the description given for a decoder, but a decoder is used to select among many devices while a demultiplexer is used to send a signal among many devices. A demultiplexer is used

Because binary numeration requires so many bits to represent relatively small numbers compared to the economy of the decimal system, analyzing the numerical states inside of digital electronic circuitry can be a tedious task. Computer programmers who design sequences of number codes instructing a computer what to do would have a very difficult task if they were forced to work with nothing but long strings of 1’s and 0’s, the �