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16.3. Comparison: Combinational vs Sequential UDPs
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Edge Notation for Sequential UDPs
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When to Use UDPs
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Simple combinational logic (2-3 inputs)
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Basic sequential elements (simple flip-flops)
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When truth/state table is simpler than code
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Educational purposes (clarity)
When to Use Modules
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Multiple outputs needed
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Vector (multi-bit) operations
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Complex logic
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Need to instantiate other components
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More than 10 inputs
16.3.2. Best Practices and Guidelines
General Guidelines
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Use descriptive names: udp_and, udp_dff (not u1, u2)
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Always initialize sequential UDPs
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Comment the truth/state table
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Test thoroughly with all input combinations
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Use don't cares (?) to simplify tables
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Document edge sensitivity clearly
Table Formatting
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Align columns for readability
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Add comments for each section
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Group related entries
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Use consistent spacing
Common Best Practices Table
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16.3.3. Common Mistakes and Solutions
Mistake #1: Forgetting reg for Sequential Output
Verilog
Mistake #2: Missing Initialization
Verilog
Mistake #3: Output Not First Port
Verilog
Mistake #4: Using Vectors
Verilog
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