2 INTRODUCTION The BCD Code The Excess-3 Code The Gray Code The ASCII CodeEncodersSeven-segment DisplaysSeven-segment LED DisplaysDecodersBCD-to-Seven-Segment Decoder/ DriverLiquid Crystal DisplaysVacuum Fluorescent Displays
3 The 8421 BCD Code Decimal number 4926 4 9 2 6 BCD stands for Binary-Coded Decimal.A BCD number is a four-bit binary group that represents one of the ten decimal digits 0 through 9.Example:Decimal number8421 BCD coded number
4 Convert the BCD coded number QUIZConvert the BCD coded numberinto decimal.BCD Coded NumberDecimal Number
5 Convert the decimal number 350 to its BCD equivalent. QUIZConvert the decimal number 350 to its BCD equivalent.Decimal NumberBCD Coded Number
6 The Excess-3 CodeAdd 3 to each digit of decimal and convert to 4-bit binary formA BCD code (not 8421 BCD)Decimal Binary Excess-3Sample Problem:DecimalExcess
7 QUIZ1. To form an excess-3 coded number, decimal 3 is added to the decimal number and this is converted to its 4-bit binary code. (True or False)True2. The excess-3 BCD number equals __________ in decimal.713. The decimal number 428 equals what excess-3 number.
8 The Gray CodeThe Gray code’s most important characteristic is that only one digit changes as you increment or decrement the count.The Gray code is commonly associated with input/output devices such as an optical encoder of a shaft’s angular position.The Gray code is NOT a BCD code.Decimal Gray code
9 QUIZ 1. The Gray code is not a type of BCD code. (True or False) True 2. The most important characteristic of the ____________ (BCD, Gray code) is that only one digit changes state as you increment or decrement the count.Gray code3. The Gray code is commonly associated with input/output devices such as an optical encoder of a shaft’s angular position. (True or False)True
10 The ASCII CodeASCII is an acronym for American Standard Code for Information InterchangeRepresents numbers, letters, punctuation marks and control charactersStandard ASCII is a 7-bit code (127 characters)Extended ASCII (IBM ASCII), an 8-bit code, is also very popularExtended ASCII adds graphics and math symbols to code (total of 256 symbols)
11 American Standard Code for Information Interchange QUIZ1. A common 7-bit code used to represent numbers, letters, punctuation marks, and control characters is known by the acronym __________.ASCII2. The acronym ASCII stands for __________________________.American Standard Code for Information Interchange3. Extended ASCII code is a(n) __________ (8-bit, 10-bit) code which adds graphic and math symbols to ASCII for a total of 256 symbols.8-bit
12 Electronic Encoder - Decimal to BCD BCD outputDecimal inputDecimaltoBCDEncoder375Encoders are available in IC form.This encoder translates from decimal input to BCD output.
13 Seven Segment Displays LED (light emitting diode) displayHigh power consumptionViewing best under low light conditionsCommonly red but available in other colorsLCD (liquid crystal display)Commonly dark characters on a silvery backgroundVery low power consumptionViewing only OK in good lightBacklighted displays can be viewed in low lightVF (vacuum fluorescent) displayCommonly blue-green display (without filters)Medium power consumptionViewing good from dark to lighter conditionsBased on vacuum tube triode technology
14 QUIZ1. The type of 7-segment display based on vacuum tube technology which usually has blue-green characters and can be viewed in dark to lighter conditions is the vacuum fluorescent display (VF). (True or False)True2. The type of 7-segment display that shows dark characters on a silvery background, uses very little power, and is good for viewing in bright light is called the liquid crystal display (LCD). (True or False)True3. The seven-segment LED display is best viewed in very bright sunlight. (True or False)False
15 7-Segment LED Display Operation Inputs7-segment code+5VagNote that inputs are“active-LOW”7-segment displayreads decimal 1(segments b & care lit)b & c inputs activethereforesegments b & clight on displayHL bL cLimiting resistorsCommon anodeCathode terminals (a thru g)7-segment LED display(common anode)
16 QUIZ H L b L c L f L g L a L b L c H L a L b L c L d L e L f L g L a H Q #3- What is the decimal output on the display for the new set of inputs?Q #4- What is the decimal output on the display for the new set of inputs?Q #2- What is the decimal output on the display for the new set of inputs?Q #1- What will be the decimal output on the 7-segment LED display?+5VagInputs7-segment codeHL bL cL fL gL aL bL cHL aL bL cL dL eL fL gL aHL cL dL fL g
17 7-Segment Decoder/Driver Decoders: BCD to7-Segment Decoder/DriverBCD inputDecimal outputLEDBCD-to-7-SegmentDecoder/DriverElectronic decoders are available in IC form.This decoder translates from BCD to decimal.Decimals are shown on an 7-segment LED display.This IC also drives the 7-segment LED display.
18 ? QUIZ Answer: 9 Answer: 7 Answer: 6 Answer: 0 Answer: 3 0 1 1 1 Q #1- What is the decimal output from the decoder thatappears on the 7-segment display?Q #4- What is the decimal output from the decoder thatappears on the 7-segment display?Q #3- What is the decimal output from the decoder thatappears on the 7-segment display?Q #5- What is the decimal output from the decoder thatappears on the 7-segment display?Q #2- What is the decimal output from the decoder thatappears on the 7-segment display?Answer: 9Answer: 7Answer: 6Answer: 0Answer: 3BCD inputDecimal outputBCD-to-7-SegmentDecoder/Driver?
19 Liquid Crystal Displays LCDs control available light (do not generate light)Nematic fluid (also called liquid crystal fluid) is sandwiched between two glass platesMonochrome twisted-nematic field-effect LCDs display dark figures on a silvery background.LCDs are commonly used on watches, calculators, and laptops. LCD monitors and TVs are becoming common.Color LCDs use either passive-matrix or active-matrix technology.Active-matrix color LCD screens are more expensive.Active-matrix color LCD screens use thin-film transistors (TFT) and red, green, blue, and white filters.Most laptop screens are backlighted for brightness.
21 QUIZ1. While VF and LED displays emit light, LCDs __________ (control available, sublimate red) light.control available2. The nematic fluid sandwiched between the glass plates of a LCD is also called _______ _______ (green phosphor, liquid crystal).liquid crystal3. Monochrome twisted-nematic field-effect LCDs display __________ (dark, white) figures on a silvery background.dark4. Liquid crystal displays are difficult to read under low light conditions however most laptop computer flat screens are backlighted to add brightness. (True or False)True
22 with out-of-phase signals Driving an LCD DisplayBCD InputabcLCDdriverdefgPhaseCommonThe LCD segmentswith out-of-phase signalsare active(a, b, & c are active)100 Hz Clock
23 ? QUIZ Q#1: What is the output on the LCD display? ANS: 2ANS: 0ANS: 5BCD InputABCDEFG?LCDDriverLCDCommon100 Hz Clock
24 Vacuum Fluorescent Displays VF displays are commonly used in automobiles because they operate at the proper voltages, have a pleasing blue-green color, are easy to see even when viewed under lower light conditions, and will operate at wide extremes of temperature.VF displays are based on an older triode vacuum tube technology.VF displays are also commonly used in point-of-sale terminals and some desktop calculators.
25 QUIZ1. A vacuum fluorescent display is based on an older vacuum tube technology and is commonly referred to as a _____ _________ (TFT display, VF display).VF display2. One of the most common applications of VF displays is in _________________ (flat-screen laptop computer screens, automobiles).automobiles3. The VF display has the advantage of being easily readable in either light or dark conditions. (True or False)True
26 Vacuum Fluorescent Display Cathodes (heaters)GridPlatesGlassbackK G f a e g d c b K
27 QUIZ Q#1- The thin wires at A are called heaters or ___. Q#2- The segments at B are called ___.Q#3- The screen like section at C is called the ___.ANS: CathodesANS: PlatesANS: GridACB
28 Operating a VF 7-Segment Display PlatesPlatesPlatesPlatesPaPbPcPdPePfPg+12 VGridGridGridGridCathodes(heaters)Cathodes(heaters)Cathodes(heaters)Cathodes(heaters)To light a segment:1. Heaters must be hot2. Grid must be at +12V3. Plate must be at +12V
29 QUIZ C A B Q#1- Part A is the ___. Q#2- Part B points at the heaters or ___.Q#3- Parts C are the ___.Q#4- The grid is normally at +12V.(T or F)ANS: gridQ#5- To light a plate it must be grounded.(T or F)ANS: cathodesQ#6- To light a plate it must be at +12V.(T or F)ANS: platesANS: TrueANS: FalseANS: TrueCABSchematic diagram of VF display with heaters connected to battery.
30 REVIEW The BCD Code The Excess-3 Code The Gray Code The ASCII Code EncodersSeven-segment DisplaysSeven-segment LED DisplaysDecodersBCD-to-Seven-Segment Decoder/ DriverLiquid Crystal DisplaysVacuum Fluorescent Displays