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1.1. Using Provided HDL Templates
1.2. Instantiating IP Cores in HDL
1.3. Inferring Multipliers and DSP Functions
1.4. Inferring Memory Functions from HDL Code
1.5. Register and Latch Coding Guidelines
1.6. General Coding Guidelines
1.7. Designing with Low-Level Primitives
1.8. Recommended HDL Coding Styles Revision History
1.4.1.1. Use Synchronous Memory Blocks
1.4.1.2. Avoid Unsupported Reset and Control Conditions
1.4.1.3. Check Read-During-Write Behavior
1.4.1.4. Controlling RAM Inference and Implementation
1.4.1.5. Single-Clock Synchronous RAM with Old Data Read-During-Write Behavior
1.4.1.6. Single-Clock Synchronous RAM with New Data Read-During-Write Behavior
1.4.1.7. Simple Dual-Port, Dual-Clock Synchronous RAM
1.4.1.8. True Dual-Port Synchronous RAM
1.4.1.9. Mixed-Width Dual-Port RAM
1.4.1.10. RAM with Byte-Enable Signals
1.4.1.11. Specifying Initial Memory Contents at Power-Up
1.6.6.1. If Performance is Important, Optimize for Speed
1.6.6.2. Use Separate CRC Blocks Instead of Cascaded Stages
1.6.6.3. Use Separate CRC Blocks Instead of Allowing Blocks to Merge
1.6.6.4. Take Advantage of Latency if Available
1.6.6.5. Save Power by Disabling CRC Blocks When Not in Use
1.6.6.6. Initialize the Device with the Synchronous Load (sload) Signal
3.4.1. Apply Complete System-Centric Timing Constraints for the Timing Analyzer
3.4.2. Force the Identification of Synchronization Registers
3.4.3. Set the Synchronizer Data Toggle Rate
3.4.4. Optimize Metastability During Fitting
3.4.5. Increase the Length of Synchronizers to Protect and Optimize
3.4.6. Increase the Number of Stages Used in Synchronizers
3.4.7. Select a Faster Speed Grade Device
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1.5.3. Latches
A latch is a small combinational loop that holds the value of a signal until a new value is assigned.
Synthesis tools can infer latches from HDL code when you did not intend to use a latch. If you do intend to infer a latch, it is important to infer it correctly to guarantee correct device operation.
Note: Design without the use of latches whenever possible.
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