The test case shows how to achieve minimum patch size by mixing Manual ECO and Automatic ECO.
The ECO case has two changes in RTL codes.
Change 1: Replace input port 'A' by 'A&B'. That is, all original fanouts of 'A' are driven by new signal 'A&B'. Signal B is also a port. So both 'A' and 'B' can be easily located in netlist. And the change can be done manually easily.
Change 2: Modify an arithmetic logic. The original 'incrementer by one' logic is replaced by 'incrementer by variable bit'. The arithmetic change is hard to be implemented by manual ECO. It is much easier to be done by tool in an automatic way.
Figure 1: Two ECO Changes
GOF uses mixed manual mode and automatic mode to implement the ECO. The two ECO changes are integrated into one ECO script.
# GofCall ECO script, eco.pl use strict; undo_eco; # Discard previous ECO operations setup_eco("mixed_eco"); # Setup ECO name read_library("m28.lib"); # Read in standard library # Read in the Reference Netlist which is re-synthesized with several modules modified read_design("-ref", "ref.v"); # Read in the implementation Netlist Which is under ECO read_design("-imp", "imp.v"); set_top("ETOP"); # Set the top module set_ignore_output("pin_sout*"); # To avoid test lockup to affect the ECO result set_pin_constant("pin_scan_en",0); # To avoid test logic being touched # The Manual ECO is to fix the change 1. Port A drives instance uvcal/place_60's in pin A. It is replaced by 'A&B' # In the example files below, Port A has name "micho_1m" and Port B has name "ops_cal_start" change_pin("uvcal/place_60/A", "SAND2X4", "uvcal/eco_11_8_16_ECOCELL_0", "-,uvcal/ops_cal_start"); # The Automatic ECO is to fix the change 2 fix_design; report_eco(); # ECO report write_verilog("eco_verilog.v"); # Write out ECO result in Verilog exit;
Three experiments have been run on the ECO case. The results are,
|ECO Result||Total Cells||Area|
|GOF (Full Automatic ECO)||31||15.0|
|GOF (Mixed Mode ECO)||15||7.1|
The files can be downloaded to reproduce the result
gof -lib m28.lib imp.v -ref ref.v -run eco.gpl
Functional netlist ECO can be complicated. Fully relying on Automatic ECO tool can not generate the optimal result. Pure manual way is hard to implement if the change involves arithmetic changes. Gates On the Fly provides a practical solution to mix manual mode and automatic mode in ECO. The solution can generate the minimum patch size in ECOs.