First Order Size Estimate
Count I/Os required
- Select FPGA with next higher number of bonded IOBs
Count flip-flops required
- Select FPGA with next smaller number of CLBs
- Capability of using two flip-flops in one CLB, or flip-flops in IOBs, may balance with combinatorial CLBs
- XC4000 allows higher utilization than XC3000
Device may be determined by special resources
- Decoder width
- Busses
- Structured logic fitting in one column (especially carry)