#97 Map tri-state buffers Issue opened by growly Yosys is not scripted to infer and map tri-state buffers. Based on a quick look at the solution implemented to #40, a similar scheme can be used to enable tri-state synthesis. I modified

scripts/synth.tcl

as follows:

diff --git a/scripts/synth.tcl b/scripts/synth.tcl
index 3f9ef60..bdfa203 100755
--- a/scripts/synth.tcl
+++ b/scripts/synth.tcl
@@ -169,6 +169,16 @@ select -clear
 
 hierarchy -check -top $vtop
 
+# Infer tri-state buffers.
+set tbuf_map false
+if { [info exists ::env(TRISTATE_BUFFER_MAP)] } {
+        if { [file exists $::env(TRISTATE_BUFFER_MAP)] } {
+                set tbuf_map true
+                tribuf
+        } else {
+          puts "WARNING: TRISTATE_BUFFER_MAP is defined but could not be found: $::env(TRISTATE_BUFFER_MAP)"
+        }
+}
 
 if { $::env(SYNTH_NO_FLAT) } {
        synth -top $vtop
@@ -182,6 +192,13 @@ opt_clean -purge
 
 tee -o "$::env(yosys_report_file_tag)_pre.stat" stat
 
+# Map tri-state buffers.
+if { $tbuf_map } {
+        puts {mapping tbuf}
+        techmap -map $::env(TRISTATE_BUFFER_MAP)
+        simplemap
+}
+
 # handle technology mapping of latches
 if { [info exists ::env(SYNTH_LATCH_MAP)] && [file exists $::env(SYNTH_LATCH_MAP)] } {
        techmap -map $::env(SYNTH_LATCH_MAP)

and then set

::env(TRISTATE_BUFFER_MAP)

to a simple mapping file in my

config.tcl

, using a (for example) Skywater 130 tri-state buffer cell:

module \$_TBUF_ (input A, input E, output Y);
  sky130_fd_sc_hd__ebufn _TECHMAP_REPLACE_ (
    .A(A),
    .Z(Z),
    .TE_B(~E));
endmodule

Note that this requires a

simplemap

to be run to map the

$not

generated by

~E

. efabless/openlane