【正文】 e used by other circuits to detect a key press. 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Encoders A1 A0 A2 A3 Show how the decimaltoBCD encoder converts the decimal number 3 into a BCD 0011. The top two OR gates have ones as indicated with the red lines. Thus the output is 0111. 1 2 3 4 5 6 7 8 9 0 0 0 0 0 0 0 0 1 0 0 1 1 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary BCD Decoder/Driver Blanked Blanked abcdefg B I / R B O0 1 0 18 4 2 1R B I L T7 4 L S 4 71abcdefg B I / R B O0 1 1 18 4 2 1R B I L T7 4 L S 4 7abcdefg B I / R B O0 0 0 08 4 2 1R B I L T7 4 L S 4 70abcdefg B I / R B O0 0 0 08 4 2 1R B I L T7 4 L S 4 70Decimal point Trailing zero suppression blanks unnecessary trailing zeros to the right of the decimal point as illustrated here. The RBI input is connected to the BI/RBO output of the following decoder. 169。 s =330 WabcdefgabcdefgM A N 7274L S 47LTBI/ RBORBI k W11223, 9, 143456778891010111112 1313141516BCD / 7 s e gBCDi npu tDCBA169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary BCD Decoder/Driver Another useful decoder is the 74LS47. This is a BCDtoseven segment display with active LOW outputs. The ag outputs are designed for much higher current than most devices (hence the word driver in the name). abcdefg1248( 1 6 )( 4 )( 1 3 )( 1 2 )( 1 1 )( 1 0 )( 9 )( 1 5 )( 1 4 )( 1 )( 2 )( 6 )( 7 )( 3 )( 5 )( 8 )BCD inputs Outputs to seven segment device GND VCC BCD/7seg BI/RBO BI/RBO LT RBI LT RBI 74LS47 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders Is the word generator set as an up counter or a down counter? (The least significant decoder output at the top). It is an up counter. 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders Inputs are blue, outputs are red. How will the waveforms change if the word generator is configured as a down counter instead of an up counter? 169。4812CS1 X/Y EN 74HC154 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Decoders IC decoders have multiple outputs to decode any bination of inputs. For example the binarytodecimal decoder shown here has 16 outputs – one for each bination of binary inputs. B i n/ D e cA00123456789101 1121314154 bi t bi na r yi nputD e c i m a lout put sA1A2A311011111111111011111For the input shown, what is the output? 169。 the second has an active LOW output. A1 A0 A2 A3 X Active HIGH decoder for 0011 A1 A0 A2 A3 X Active LOW decoder for 0011 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Comparators IC parators can be expanded using the cascading inputs as shown. The lowest order parator has a HIGH on the A = B input. Outputs A1 A0 A2 A3 B1 B0 B2 B3 COMP A = B A B A B A = B A B A B 0 0 3 3 A A A5 A4 A6 A7 B5 B4 B6 B7 + V COMP A = B A B A B A = B A B A B 0 0 3 3 A A LSBs MSBs 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Comparators The function of a parator is to pare the magnitudes of two binary numbers to determine the relationship between them. In the simplest form, a parator can test for equality using XNOR gates. How could you test two 4bit numbers for equality? AND the outputs of four XNOR gates. A1 B1 A2 B2 A3 B3 A4 B4 Output 169。 2022 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved Floyd, Digital Fundamentals, 10th ed Summary Parallel Adders Full adders are bined into parallel adders that can add binary numbers with multiple bits. A 4bit adder is shown. A B S Cout Cin A B S Cout Cin A B S Cout Cin A B S Cout Cin A1 B1 S1 C0 S2 S3 S4 C1 C2 C3 C4 A2 B2 A3 B3 A4 B4 The output carry (C4) is not ready until it prop