【正文】 ry Decoders A 0 = 0A 1 = 1A 2 = 0A3 = 11Assume the output of the decoder shown is a logic 1. What are the inputs to the decoder? 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders A specific integrated circuit decoder is the 74HC154 (shown as a 4to16 decoder). It includes two active LOW chip select lines which must be at the active level to enable the outputs. These lines can be used to expand the decoder to larger inputs. CS2 A1 A0 A2 A3 1512131412349101156780amp。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders The 74LS138 is a 3to8 decoder with three chip select inputs (two active LOW, one active HIGH). In this Multisim circuit, the word generator (XWG1) is set up as an up counter. The logic analyzer (XLA1) pares the input and outputs of the decoder. Inputs are blue, outputs are red. 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders The chip select inputs can be used to expand a decoder. In this circuit, two 74LS138s are configured as a 16 line decoder. Notice how the MSB is connected to one active LOW and one active HIGH chip select. The next slide shows the logic analyzer output… 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders BCDtodecimal decoders accept a binary coded decimal input and activate one of ten possible decimal digit indications. B C D / D E C012345678912487 4 H C 4 2( 1 1 )( 1 0 )( 9 )( 7 )( 6 )( 5 )( 4 )( 3 )( 2 )( 1 )( 1 5 )( 1 4 )( 1 3 )( 1 2 )A1 A0 A2 A3 Assume the inputs to the 74HC42 decoder are the sequence 0101, 0110, 0011, and 0010. Describe the output. All lines are HIGH except for one active output, which is LOW. The active outputs are 5, 6, 3, and 2 in that order. 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary BCD Decoder/Driver Here the 7447A is an connected to an LED seven segment display. Notice the current limiting resistors, required to prevent overdriving the LED display. VCCGND+ V+ VR 39。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary BCD Decoder/Driver abcdefg B I / R B O0 0 0 08 4 2 1R B I L T07 4 L S 4 7abcdefg B I / R B O0 0 0 08 4 2 1R B I L T07 4 L S 4 7abcdefg B I / R B O0 0 1 18 4 2 1R B I L T07 4 L S 4 7abcdefg B I / R B O0 0 0 08 4 2 1R B I L T17 4 L S 4 7Blanked Blanked The 74LS47 features leading zero suppression, which blanks unnecessary leading zeros but keeps significant zeros as illustrated here. The BI/RBO output is connected to the RBI input of the next decoder. Depending on the display type, current limiting resistors may be required. 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Encoders An encoder accepts an active logic level on one of its inputs and converts it to a coded output, such as BCD or binary. The decimal to BCD is an encoder with an input for each of the ten decimal digits and four outputs that represent the BCD code for the active digit. The basic logic diagram is shown. There is no zero input because the outputs are all LOW when the input is zero. A1 A0 A2 A3 1 2 3 4 5 6 7 8 9 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Encoders The 74HC147 is an example of an IC encoder. It is has ten activeLOW inputs and converts the active input to an activeLOW BCD output. This device is offers additional flexibility in that it is a priority encoder. This means that if more than one input is active, the one with the highest order decimal digit will be active. Decimal input BCD output 1248( 1 6 )( 1 1 )( 1 2 )( 1 3 )( 1 )( 2 )( 4 )( 3 )( 5 )( 9 )( 7 )( 6 )( 1 4 )( 8 )12345678( 1 0 )9GND VCC HPRI/BCD 74HC147 The next slide shows an application … 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Code converters There are various code converters that change one code to another. Two examples are the fou