DIGITAL ELECTRONICS

THE LATCHES Combinational circuits are characterized by the fact that the output is the logical result of the signals present at the input at the same instant without considering propagation delays. A sequential circuit, on the other hand, also stores the previously assumed states in addition to those currently present at the input . There is a feedback which sends the output signal towards the input . In this type of circuit there is a memorization mechanism of the previous states which condition the following ones. These stored states are called internal variables, and the ability of a sequential [...]

TIMED LOGIC In wider contexts when digital circuits have to communicate with each other, it is necessary to synchronize the data transfer, also considering the delays that a given circuit can produce. This synchronization or clock is generally obtained by an astable multivibrator which, as we have seen, has no stable state but oscillates by means of RC circuits, producing a square or rectangular wave output. In microprocessors, synchronization is based on quartz circuits, they offer greater stability and much higher working frequencies. EDGE TRIGGED So far we have seen how digital circuits are activated by two reference voltages, [...]

ELECTRONIC COUNTERS INTRODUCTION Electronic counters are made using a chain of flip-flops with NET (Negative Edge Trigged) clock inputs. Based on the number of stages used, the set of outputs for example QA, QB, Qn produces at each clock pulse a binary number equivalent to the number of pulses received. A three-stage counter is called an 8 module as it is able to count from 0 to 7 23 = 8. The binary numbering obtained at the flip-flop output must be interpreted from left to right, that is Qn, QB, QA where the output of the first QA is [...]

7-SEGMENT DISPLAY One way to visualize the numbers is through this type of display where every access led in the right combination makes the decimal number appear. Each segment of the display is an LED along with a limiting resistor. There are two large types of 7-segment displays, those with common anode (AC) and those with common cathode (CC). 7-SEGMENT BCD DECODING To be able to read a number, so-called decoders are used, in particular in our case a "BCD-7 Segments" decoder which converts the binary input into a combination of seven outputs that turn on [...]