Using Carry Chains in Your Design
Number of Chains
- No More Than 20% of FLEX Device Should Use Carry Chains
Length of Each Chain
- Maximum Length Should Be 32 LEs for Performance
- For Ripple-Carry Longer than 32 LEs, Consider Carry Look-Ahead or Carry-Select Implementations to Improve Performance
- Carry Chains Longer Than 32 LEs May Still Provide Utilization Advantages
Further Reading
- AN 36: Designing with FLEX 8000 Devices
- MAX+PLUS II Online Help: Search on “Carry”