add code-comments regarding potential use of FFSynchroniser

diff --git a/c4m/nmigen/jtag/tap.py b/c4m/nmigen/jtag/tap.py
index a72c89a0956f25b41e9fb10ed088f3844afd0b84..77034cbc3040a20e814fd73c48801450873667f7 100755 (executable)
--- a/c4m/nmigen/jtag/tap.py
+++ b/c4m/nmigen/jtag/tap.py
@@ -510,6 +510,7 @@ class TAP(Elaboratable):
                 with m.State("READACK"):
                     with m.If(dmi.ack_o):
                         # Store read data in sr_data.i hold till next read
+                        # Note: could use FFSynchroniser
                         cd += sr_data.i.eq(dmi.dout)
                         m.next = "IDLE"
 
@@ -662,6 +663,7 @@ class TAP(Elaboratable):
             # clockdomain latch update in `domain` clockdomain and see when
             # it has falling edge.
             # At that edge put isir in sr.oe for one `domain` clockdomain
+            # Note: could use FFSynchroniser instead
             update_core = Signal(name=sr.name+"_update_core")
             update_core_prev = Signal(name=sr.name+"_update_core_prev")
             m.d[domain] += [
@@ -678,6 +680,7 @@ class TAP(Elaboratable):
             with m.If(sr_shift):
                 m.d.posjtag += reg.eq(Cat(reg[1:], self.bus.tdi))
             with m.If(sr_capture):
+                # could also use FFSynchroniser here too
                 m.d.posjtag += reg.eq(sr.i)
 
             # tdo = reg[0], tdo_en = shift
@@ -776,8 +779,8 @@ class TAP(Elaboratable):
                             m.next = "READACK"
                 with m.State("READACK"):
                     with m.If(wb.ack):
-                        # Store read data in sr_data.i
-                        # and keep it there til next read
+                        # Store read data in sr_data.i and keep it there
+                        # til next read. could use FFSynchroniser (see above)
                         m.d[domain] += sr_data.i.eq(wb.dat_r)
                         m.next = "IDLE"
                 with m.State("WRITEREAD"):