Merge pull request #1690 from bunnie/asic-target

add an option to generate without reg initializers (asic targets)

litex/gen/fhdl/verilog.py

@@ -421,7 +421,7 @@ def _print_module(f, ios, name, ns, attr_translate):
 
     return r
 
-def _print_signals(f, ios, name, ns, attr_translate):
+def _print_signals(f, ios, name, ns, attr_translate, asic=False):
     sigs = list_signals(f) | list_special_ios(f, ins=True, outs=True, inouts=True)
     special_outs = list_special_ios(f, ins=False, outs=True,  inouts=True)
     inouts       = list_special_ios(f, ins=False, outs=False, inouts=True)
@@ -434,7 +434,10 @@ def _print_signals(f, ios, name, ns, attr_translate):
         if sig in wires:
             r += "wire " + _print_signal(ns, sig) + ";\n"
         else:
-            r += "reg  " + _print_signal(ns, sig) + " = " + _print_expression(ns, sig.reset)[0] + ";\n"
+            if asic:
+                r += "reg  " + _print_signal(ns, sig) + ";\n"  # ASICs can't assign an initial value to a reg, it is always X
+            else:
+                r += "reg  " + _print_signal(ns, sig) + " = " + _print_expression(ns, sig.reset)[0] + ";\n"
     return r
 
 # ------------------------------------------------------------------------------------------------ #
@@ -532,6 +535,8 @@ def convert(f, ios=set(), name="top", platform=None,
     # Sim parameters.
     time_unit      = "1ns",
     time_precision = "1ps",
+    # Generate for ASIC simulation (i.e. capture X-on-init for regs)
+    asic = False,
     ):
 
     # Build Logic.
@@ -618,7 +623,7 @@ def convert(f, ios=set(), name="top", platform=None,
 
     # Module Signals.
     verilog += _print_separator("Signals")
-    verilog += _print_signals(f, ios, name, ns, attr_translate)
+    verilog += _print_signals(f, ios, name, ns, attr_translate, asic)
 
     # Combinatorial Logic.
     verilog += _print_separator("Combinatorial Logic")