comment on why clocks are in FSM

diff --git a/c4m/nmigen/jtag/tap.py b/c4m/nmigen/jtag/tap.py
index a997554fba6871c4c436ad923cfe51287ac06089..525b5311748973a4b287516154e8759b4e3f0710 100755 (executable)
--- a/c4m/nmigen/jtag/tap.py
+++ b/c4m/nmigen/jtag/tap.py
@@ -25,6 +25,7 @@ class _FSM(Elaboratable):
         self.shift = Signal()
         self.update = Signal()
 
+        # JTAG uses both edges of the incoming clock (TCK). set them up here
         self.posjtag = ClockDomain("posjtag", local=True)
         self.negjtag = ClockDomain("negjtag", local=True, clk_edge="neg")