MadSci Network: Computer Science |
Hello Navarra: Calculators are based on Very Large-Scale Integrated (VLSI) microcircuits composed of logic and state transition elements and microcoded so that with a few pushes of buttons one can accomplish marvelous results. Our biggest drawback with microcircuits is the access needed to inject and extract signals in a small package. http://encarta.msn.com/find/Concise.asp?ti=0494F000 Computers unlike people prefer to calculate numbers using binary bases because of the fundamental logical values are 0 and 1 (forget for the moment fuzzy logic). Serial to parallel shift registers demonstrates how a number can be multiplied by two with a single shift from the least significant bit towards the most significant bit. Let us assume an 8-bit binary shift register. Bit 0, the least significant bit, is loaded with a logic level 1, or high. As it is shifted toward bit 7, it is incremented by the power of two on each shift. So we start with 1, shift by one and the value becomes 2. The next shift the value becomes 4, and so on until the last shift produces 64. One additional shift produces 0 unless that bit is carried around to bit 0, in which case its value is one again. Look at this site for specifications of a typical binary shift register: http://www.ednmag.com/reg/1995/010595/01di6.htm#fig1 http://www.fairchildsemi.com/ds/MM/MM74HC594.pdf At one Internet site I found has pictures of very simple digital circuits: http://www2.pct.edu/homepage/staff/rstull/DIGITAL/DIGITAL.HTM I also found another site you might look-up: www.hobby-electronics.com/Counter10-100-1000.htm It describes 3 low power common CMOS chips hooked-up to give a count indication of 10s, 100s and thousands of pulses at the input. If you used a 5-volt power supply and 470 ohm resistors to limit current for the LEDs, the outputs give a visual indication of the number of 10s, 100s and thousands. A third and better site shows an actual counter circuit with leds: www.interq.or.jp/japan/se-inoue/e_ckt14.htm Exercise care when handling integrated circuits: they are very susceptible to Electro-Static Discharge (ESD). In a dry day a person may easily accumulate 5 to ten thousand volts by shoe-to-carpet friction or polyester fabric friction. These voltages are hardly noticeable to us but very destructive to the tiny components and micro-traces inside the silicon chip. Always place your unprotected parts on a conductive surface that is grounded. Be sure to place a hand on that surface to equalize your body potential before handling the chip. Do a search on the Internet for “ESD” and you will discover how important it is to prevent ESD damage. Your MAD.SCI Micro.
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