ITEC 352 Lecture 5 Low level components(3)

Low level components Review Multiplexers Demultiplexer Minterm/Maxterm Karnaugh Map

Low level components Outline Decoders 7 Segment display

Low level components Decoder Similar to a DeMultiplexer –Essential difference: the select (or control lines) are now considered as part of input. Used to convert logical encoding into spatial encoding. Decoders generate the minterms for a function.

Low level components A 2-4 Decoder: generates all possible minterms with 2 bits

Low level components Majority Function Implement it using a decoder

Low level components Using a Decoder to Implement the Majority Function

Low level components Example decoder Example:Develop a circuit for this: Develop a circuit that drives one input digit for this clock radio.

Low level components Clock radio Step 1: –Initial questions: How many outputs are there for the circuit ? How many inputs are needed to design this circuit ? –Usually we are interested only in the minimum number of inputs. –However, sometimes it helps us look at other inputs. »What possible other inputs can you think of ? Next: How are the outputs related to the inputs.

Low level components numeric display (2) How are the outputs related to the inputs ? –Capture this function using a boolean equation –How do we derive boolean equations? use truth tables. a b d c e f g

Low level components numeric display (3) Draw the truth table for matching inputs to outputs.

Low level components numeric display (4) Which of the following standard circuits can you use to develop this circuit: –Decoder –Multiplexer –Demultiplexer Why ?

Low level components numeric display (5) Decoders generate minterms. What type of a decoder would you use: –1 X 2 –2 X 4 –3 X 8 –Etc.. ?

Low level components Implementatio n Logisim demonstration

Low level components Review Decoders Majority function