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EE365 Adv. Digital Circuit Design Clarkson University

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HW#4 Help Rissacher EE365 Be aware of proper Bit order A A ? Not Necessarily MSB MSB LSB LSB

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HW#4 Help Rissacher EE365 Device Circuit Description

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HW#4 Help Rissacher EE365 MSB

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More VHDL Projects will get more complex (devices and circuits will be more difficult to define) In Proj #3, don’t worry about “minimization” of circuit, just make it work with MSI devices… there may be more than one way to create a successful device However, complexity of your design will be considered in the grade (overly large circuits will lose some points) May need to learn some more VHDL syntax

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VHDL: Concatenation Given several bits (e.g., A0, A1, A2), they can be concatenated using the ‘&’ operator For example: A0 = ‘1’ A1 = ‘0’ A2 = ‘0’ (A0 & A1 & A2) = ‘100’

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VHDL: Concatenation Concatenated terms can be used for relational operations For example: F <= ‘1’ after 20ns when (A0 & A1 & A2) = ‘100’ …

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VHDL: More Complex Devices MSI devices are more complex and will be harder to define. The may have several inputs and several outputs For each output, use a separate concurrent statement For example: F <= ‘1’ after 20ns when (A0 & A1 & A2) = ‘100’ else ‘0’ after 20 ns; G ‘000’ else ‘0’ after 40 ns;

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VHDL: More Complex Devices May need very long statements to define all of the possibilities that drive a certain output For example: F <= ‘1’ after 20 ns when (A=‘1’) or (B=‘1’) or (C=‘1’) or ((D=‘1’)and(EN_L=‘0’)) or (BYP_L = ‘0’) else ‘0’ after 60 ns; (And they can get much worse)

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VHDL ELEC 311 Digital Logic and Circuits Dr. Ron Hayne Images Courtesy of Cengage Learning.

VHDL ELEC 311 Digital Logic and Circuits Dr. Ron Hayne Images Courtesy of Cengage Learning.

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