NanDigits Design Automation

Timing ECO Use Case

In Netlist Time Closure period, the timing violation report file can be huge and hard to read.

GOF can parse Synopsys Primetime timing violation report file efficiently.

Users can select to draw the cells and connections in a violated path on a schematic.

On the schematic, find the critical cells and do proper ECO operations.

Resize or split the cells to speed up the path.

Or delay the target clock to shift timing to next stage.

Important! To generate the Prime Time report_timing with -nosplit option.

Launch "PT Violations Controller".

PT Violations Controller window pops up.

Input Report File and parse.

Click Summary button to select list "All Violations" or "List bottlenecks".

Here is all violations.

Click Summary button and on pop-up menu select 'List bottlenecks'.

Here is the bottleneck report.

In 'Through Point' Item, select one of the point appearing in the above bottleneck report.

Click PathsDetail button to see detail report from the original Primetime report file.

Here is the list.

Click Display button, the three path which go through U4957 are drawn on GofTrace schematic.

Zoom-out, select path1 text, the whole path 1 cells are highlighted.

Click Path2 text, the whole path2 cells are highlighted.

Click Path3 text, the whole path3 cells are highlighted.

You can choose to display more paths on the existing schematic or new schematic.
Click Display button, a pop-up menu is for you to select.

You can also exclude some paths.
Click Exclude button.

Type in the point you would like to exclude from list. Wild card is acceptable.

The Exclude button becomes red to warn something is excluded by user.
And the Start Point is not in the list any more.

Click Display button to draw the worst path excluding the path defined by exclude option.

Enable ECO mode by check ECO check-button.
Increase some cells' drive capability. uinst_hshf.U6826 and uinst_hshf.U4953 from X2 to X4.

The instance uinst_hshf.curindex_reg_3_ is shared by three paths and has big fanouts and cell-delay. Create another cell to off-load some fanouts.
Select 3 connections which drive 5 fanouts. Click ECO button 'Insert cells into connections'.

Choose 'One ECO cell drives multiple lines'. Click Ok.

Enter 1 for cell number. Click Ok.

Choose same cell type p_SDFFRHQX4. Click Ok.

Choose same connections as the original instance. Click OK.

The ECO cell and connections are below.

Change the ECO instance name by cell edit. Click Save ECO button.

Check ECO result in Synopsys TCL format.

current_design TM_P_sf
disconnect_net [get_nets test_shf[3]] [get_pins add_438/A[3]]
disconnect_net [get_nets test_shf[3]] [get_pins sub_521/A[3]]
disconnect_net [get_nets test_shf[3]] [get_pins add_522/A[3]]
change_cell_size U6826 tsmc90lp_hv.synth/MXI2X4
change_cell_size U4953 tsmc90lp_hv.synth/NAND2BX4
create_cell eco012345_split_curindex_reg_3_ tsmc90lp_hv.synth/p_SDFFRHQX4
create_net test_shf_3__eco012345_0
connect_net [get_nets test_shf_3__eco012345_0] [get_pins add_438/A[3]]
connect_net [get_nets test_shf_3__eco012345_0] [get_pins sub_521/A[3]]
connect_net [get_nets net110395] [get_pins eco012345_split_curindex_reg_3_/CK]
connect_net [get_nets gbrstn] [get_pins eco012345_split_curindex_reg_3_/RN]
connect_net [get_nets test_shf_3__eco012345_0] [get_pins eco012345_split_curindex_reg_3_/Q]
connect_net [get_nets N469] [get_pins eco012345_split_curindex_reg_3_/D]
connect_net [get_nets test_shf_3__eco012345_0] [get_pins add_522/A[3]]