Synthesizability Considerations
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Synthesizable Loops (for loop only)
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For loops can be synthesized ONLY under these conditions:
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Loop bounds must be CONSTANTS known at elaboration
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Iteration count must be determinable at compile time
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Loop is 'unrolled' into replicated hardware
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No timing controls inside loop body
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Synthesizable Example
Verilog
Non-Synthesizable Loops
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Best Practices and Guidelines
Loop Selection Guide
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Use for: Array operations, when you need the index value
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Use while: When iteration count depends on a condition
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Use repeat: For simple N-time repetition, waiting N cycles
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Use forever: For clock generation and continuous monitoring
General Best Practices
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Always use integer for loop variables
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Include timing controls in while/forever loops
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Use begin-end even for single statements (clarity)
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Avoid deep nesting (max 2-3 levels)
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Comment complex loop logic
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Use parameters for loop bounds in synthesizable code
Synthesis Guidelines
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Only use for loops in synthesizable code
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Ensure loop bounds are constants
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Keep iteration count reasonable for hardware size
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Remember: loops unroll to replicated logic
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Test synthesis results for large loop counts
Complete Testbench with All Loop Types
Verilog
Common Mistakes and Solutions
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Mistake #1: Infinite Zero-Time Loop
Verilog
Mistake #2: Using reg for Loop Variables
Verilog
Mistake #3: Variable Loop Bounds in Synthesis
Verilog
Mistake #4: Forgetting begin-end
Verilog