diff --git a/litex/build/altera/quartus.py b/litex/build/altera/quartus.py index e8d01c909..b71dfd73d 100644 --- a/litex/build/altera/quartus.py +++ b/litex/build/altera/quartus.py @@ -226,9 +226,11 @@ class AlteraQuartusToolchain: def add_period_constraint(self, platform, clk, period): clk.attr.add("keep") + period = math.floor(period*1e3)/1e3 # round to lowest picosecond if clk in self.clocks: - raise ValueError("A period constraint already exists") - period = math.floor(period*1e3)/1e3 # Round to lowest picosecond + if period != self.clocks[clk]: + raise ValueError("Clock already constrained to {:.2f}ns, new constraint to {:.2f}ns" + .format(self.clocks[clk], period)) self.clocks[clk] = period def add_false_path_constraint(self, platform, from_, to):