if no wb stall assume single-cycle mode

diff --git a/c4m/nmigen/jtag/tap.py b/c4m/nmigen/jtag/tap.py
index 4be95578eb38869dc161e159e23d00941c936e0d..caf2ce41a9bf4b044faa1bc22a4bb0aea6d9ea3c 100755 (executable)
--- a/c4m/nmigen/jtag/tap.py
+++ b/c4m/nmigen/jtag/tap.py
@@ -786,8 +786,17 @@ class TAP(Elaboratable):
                         m.d[domain] += wb.adr.eq(wb.adr + 1)
                         m.next = "READ"
 
+                if hasattr(wb, "stall"):
+                    m.d.comb += wb.stb.eq(fsm.ongoing("READ") |
+                                          fsm.ongoing("WRITEREAD"))
+                else:
+                    # non-stall is single-cycle (litex), must assert stb
+                    # until ack is sent
+                    m.d.comb += wb.stb.eq(fsm.ongoing("READ") |
+                                          fsm.ongoing("WRITEREAD") |
+                                          fsm.ongoing("READACK") |
+                                          fsm.ongoing("WRITEREADACK"))
                 m.d.comb += [
                     wb.cyc.eq(~fsm.ongoing("IDLE")),
-                    wb.stb.eq(fsm.ongoing("READ") | fsm.ongoing("WRITEREAD")),
                     wb.we.eq(fsm.ongoing("WRITEREAD")),
                 ]