1. ASIC PROTOYPING ON FPGA Zvi Goldenberg Engineer at Intel Senior Lecturer at Logtel May 4, 2011

2. Methodology and Challenges Very few code modifications Compromise readiness Identifying our customer ! (sw, design, be ) Define priorities – what is covered well by verification team ? Should I verify external IP’s ? Good system partition

3. Methodology and Challenges Lower system clocks (flow control may be used) Reduce design & synthesis cycle times (use compile point, FPGA editor etc.)

4. Clock tree modification

5. Simplifying clock tree Use FPGA PLL/MMCM by coregen Instantiate BUFG/BUFGCE/BUFGMUX Delete test mode clocking Use “fix gated clock” carefully Consider bypass clock gaters Refer to “gated clock” warning

6. System partitioning Try to locate FF at I/O pads (otherwise, in/out pad delay will reduce dramatically system performance) To save pin count: connect DDR/QDR/serdes between units (Adds latency , check if possible) Usually , phase of 2 FPGA’s must be equal Use PLL carefully to adjust Assign clk_FPGA_1_to_FPGA_2 = sys_clk_FPGA_1 won’t work – why ? Cont…

7. System partitioning Inter-connection pins : ddr/qdr/serdes may be added between units to save pins Tip : consider GTX serdes connection between 2 FPGA’s . This will enable system expansion. Tip : connect _gc pins from FPGA-1 to FPGA_2 to eliminate parasitic input delay on clock pins.

8. Reviewing reports Do I have slacks ? Are all pins located ? Are all pins got drive level + correct standard ? Did I constraint all clocks ? Answer: Run trce with –u Did I constrained all I/O’s offset ? - Same Do I understand all clock tree ? Search for derived clocks Cont…

9. Reviewing reports Do I have local clocks with large skew ? Did the tool understand my timing exceptions ? What is sampling window of main interfaces ? Answers can be found in .twr + .par + .csv reports Cont…

10. Reviewing reports I changed only version number and design stopped working !!! Possible reasons :

11. FPGA editor usage Invert input signal DCM /PLL Phase shift adjustment(manual calibration) Add pullup/down to pad Change drive level Change init value of FF/RAM Change logic equation of LUT add probes

12. Synthesis warning example case 0 case 1 … case 9 case 0 case 11.. case 19 Warning : case repetition

13. BUG example

14. TX RACE Inactive state must be ‘1’ (held by pull-up) when oen ↓ (close tx buffer) , input 1 of AND gate is driven to 0 >> data out_pad ==0 300 ps later buffer is closed >> data ↑ by pull-up (very slowly) Result : glitch detected by RX logic !!!!!!!! Found in Customer site 