openroad: insert scan_chain

Author: TheMightyDuckOfDoom

openroad/scripts/01_floorplan.tcl

@@ -41,6 +41,12 @@ utl::report "Read netlist: ${netlist}"
 read_verilog $netlist
 link_design $top_design
 
+utl::report "Read DFT configuration"
+source src/dft_config.tcl
+
+utl::report "Insert scan flip-flops"
+scan_replace
+
 utl::report "Read constraints"
 read_sdc src/constraints.sdc
 

openroad/scripts/02_placement.tcl

@@ -51,6 +51,9 @@ utl::report "Repair tie fanout"
 repair_tie_fanout $tieHiPin 
 repair_tie_fanout $tieLoPin 
 
+utl::report "Read DFT configuration"
+source src/dft_config.tcl
+
 utl::report "Remove buffers"
 remove_buffers
 
@@ -112,6 +115,9 @@ detailed_placement
 utl::report "Optimize mirroring"
 optimize_mirroring
 
+utl::report "Stitch Scan Chain"
+execute_dft_plan
+
 utl::report "Estimate parasitics"
 estimate_parasitics -placement
 

openroad/src/constraints.sdc

@@ -87,6 +87,8 @@ set_input_delay -max [ expr $TCK_JTG * 0.10 ] [get_ports {rst_ni testmode_i}]
 set_false_path -hold   -from [get_ports {rst_ni testmode_i}]
 set_max_delay $TCK_SYS -from [get_ports {rst_ni testmode_i}]
 
+set_input_delay -min -add_delay -clock clk_sys [ expr $TCK_SYS * 0.10 ] [get_ports scan_en_i]
+set_input_delay -max -add_delay -clock clk_sys [ expr $TCK_SYS * 0.10 ] [get_ports scan_en_i]
 
 ##########
 ## JTAG ##

openroad/src/dft_config.tcl

@@ -0,0 +1,22 @@
+# Copyright 2026 ETH Zurich and University of Bologna.
+# Solderpad Hardware License, Version 0.51, see LICENSE for details.
+# SPDX-License-Identifier: SHL-0.51
+
+# Authors:
+# - Tobias Senti <tsenti@ethz.ch>
+
+## Scan chain configuration
+
+# max_chains: 1 scan chain per clock domain (clk_i and jtag_tck_i)
+# scan_enable_name_pattern: Connecto to p2c pin of pad_scan_en_i
+# scan_in_name_pattern: Connect to p2c pin of pad_gpio{}_io (0 and 1)
+# scan_out_name_pattern: Connect to A1 pin of i_scan_out_mux_{} (0 and 1)
+
+set_dft_config\
+	-max_chains 1 \
+	-scan_enable_name_pattern pad_scan_en_i/p2c \
+	-scan_in_name_pattern pad_gpio{}_io/p2c \
+	-scan_out_name_pattern i_scan_out_mux_{}/A1
+
+# Report config
+report_dft_config

openroad/src/padring.tcl

@@ -131,7 +131,7 @@ place_pad -row IO_NORTH -location [expr {$northStart -  9*$northPitch}] "pad_gpi
 place_pad -row IO_NORTH -location [expr {$northStart - 10*$northPitch}] "pad_unused0_o"       ; # pin no: 11
 place_pad -row IO_NORTH -location [expr {$northStart - 11*$northPitch}] "pad_unused1_o"       ; # pin no: 12
 place_pad -row IO_NORTH -location [expr {$northStart - 12*$northPitch}] "pad_unused2_o"       ; # pin no: 13
-place_pad -row IO_NORTH -location [expr {$northStart - 13*$northPitch}] "pad_unused3_o"       ; # pin no: 14
+place_pad -row IO_NORTH -location [expr {$northStart - 13*$northPitch}] "pad_scan_en_i"       ; # pin no: 14
 place_pad -row IO_NORTH -location [expr {$northStart - 14*$northPitch}] "pad_vss3"            ; # pin no: 15
 place_pad -row IO_NORTH -location [expr {$northStart - 15*$northPitch}] "pad_vdd3"            ; # pin no: 16