A Practical Way to Do Netlist ECO & Debug

Contents

  1. Abstract
  2. Prepare GUI environment
  3. Find related gates on the schematic
  4. Find physical position of the logic under fix
  5. Circuit on LayoutViewer
  6. Find physical position of the enable logic on LayoutViewer
  7. Two related circuits on LayoutViewer
  8. Zoom view of LayoutViewer
  9. Find proper spare gates and send to schematic
  10. All resources on schematic
  11. Enable ECO
  12. Clean up spare gates
  13. Disconnect wire for AND gate insertion
  14. Connect up spare gates
  15. One connection done
  16. All connected up and save ECO
  17. Report window
  18. Verify the fix
  19. View ECOed circuit on LayoutViewer

GUI Mode Metal Only ECO

Abstract

In the traditional way, Metal ECO has to go back and forth between backend database and frontend netlist under ECO. A simple AND gate insertion logic fix needs intensive search for spare resource in backend database. Gates On the Fly combines the resource search and logic fix in one platform. The following use case shows how to read in physical database into Gates On the Fly, and finds the proper spare gates to fix an AND logic insertion.

The logic change is very simple, adding an AND gate to one output signal, but the enable signal for the AND gate may have some distance. Spare buffers may be needed to drive the enable signal.

Prepare GUI environment

Load in netlist and physical files by the command

../bin/gof -lib tm40.lib -def tser_post.def -lef tm_hvt.lef tser_post.v

When GofViewer Netlist browser window is up, find the related net and click 'New Schematic' button.

Figure 1. Load GUI database and bring up schematic

Starting from the port, 'tseran_int0', use mouse-middle-button to trace the gates. Load the enable signal 'rx_mode' to the schematic as well and trace to make a proper circuit.

The logic change is essentially, "tseran_int0 = original_tseran_int0 & rx_mode"

Figure 2. Load related gates and signals

Find physical position of the logic under fix

Select the circuit under fix, right click mouse to select 'Copy Selected to' -> 'Layout New'

Figure 3. Send circuit to LayoutViewer

Circuit on LayoutViewer

The circuit is shown on LayoutViewer as lines and arrows.

Click to select another color when the first circuit is shown on LayoutViewer. So the new circuit view will be displayed in different color.

Figure 4. LayoutViewer 1

Find physical position of the enable logic on LayoutViewer

Select the enable logic circuit and send to the same LayoutViewer Index

Figure 5. Send enable logic to LayoutViewer

Now two circuits are on one LayoutViewer. Find the closest part of them, spare gates will be found in that part.

Figure 6. Two related circuits shown on the same LayoutViewer

Zoom view of LayoutViewer

Zoom in to closest part between two circuits. Proper spare gates will be found in this area.

Figure 7. Zoom-in to the right place

Find proper spare gates and send to schematic

Select color 'green'.

Type 'mySpare*/*spr_gate*' in the bottom Search entry and high light all spare gates on the LayoutViewer.

Spare gates have type NAND NOR MUX INV, so AND gate has to be NAND+INV. A buffer is needed to drive 'rx_mode' signal from the circuit in orange. The buffer can be created from two back to back inverts.

So total 3 inverters and one NAND gate are needed.

Find NAND and INV gate close to the circuit in blue. 'mySpare_tserspr_23.NAND2_X4M_spr_gate326' and 'mySpare_tserspr_16.INV_X9M_spr_gate235'

Find big driver INV close to orange circuit, 'mySpare_tserspr_32.INV_X9M_spr_gate458'. Find another INV in between blue and orange circuits, 'mySpare_tserspr_23.INV_X9M_spr_gate333'

These two inverts are connected back to back to create a buffer.

Figure 8. Spare gates process on LayoutViewer

All resources on schematic

Figure 9. Spare gates on schematic

Enable ECO

Figure 10. Enable ECO

Clean up spare gates

Trace inputs to spare gates and delete the connections.

Figure 11. Delete spare gates inputs

Disconnect wire for AND gate insertion

The best place to insert AND gate is NAND4 output which is closest to the enable signal 'rx_mode'

Figure 12. Disconnect ECO spot

Connect up spare gates

Press mouse-middle-button on a spare input pin, don't release the button and move the button to the other gate's output pin it should connect to. Then release the button.

Figure 13. Wire connecting

One connection done

One connection is done and ports are automatically added to bridge up the hierarchies.

Figure 14. Connection done

All connected up and save ECO

Save the ECO in verilog mode, 'tser_eco.v'

Figure 15. ECO complete schematic

Report window

Figure 16. ECO report

Verify the fix

Load tser_eco.v and related physical files.

../bin/gof -lib tm40.lib -def tser_post.def -lef tm_hvt.lef tser_eco.v

Draw the related circuit and send to a new LayoutViewer.

Figure 17. Draw complete circuit

View ECOed circuit on LayoutViewer

Compare with figure 6, it's easy to see the spare gates used and connections are in the right location.

Figure 18. ECO verified on LayoutViewer

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