From 81e311b503cee4d9edcf6f9ec7eb8f1a095d0505 Mon Sep 17 00:00:00 2001
From: Staf Verhaegen <staf@stafverhaegen.be>
Date: Fri, 6 Dec 2019 20:06:49 +0100
Subject: [PATCH] Simplify signal generation for TAP wishbone interfaces.

---
 c4m/nmigen/jtag/tap.py | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/c4m/nmigen/jtag/tap.py b/c4m/nmigen/jtag/tap.py
index 333105d..a723ab2 100755
--- a/c4m/nmigen/jtag/tap.py
+++ b/c4m/nmigen/jtag/tap.py
@@ -309,11 +309,6 @@ class TAP(Elaboratable):
 
             with m.FSM(domain=domain) as fsm:
                 with m.State("IDLE"):
-                    m.d.comb += [
-                        wb.cyc.eq(0),
-                        wb.stb.eq(0),
-                        wb.we.eq(0),
-                    ]
                     with m.If(sr_addr.oe): # WBADDR code
                         m.d[domain] += wb.adr.eq(sr_addr.o)
                         m.next = "READ"
@@ -325,37 +320,23 @@ class TAP(Elaboratable):
                         m.d[domain] += wb.dat_w.eq(sr_data.o)
                         m.next = "WRITEREAD"
                 with m.State("READ"):
-                    m.d.comb += [
-                        wb.cyc.eq(1),
-                        wb.stb.eq(1),
-                        wb.we.eq(0),
-                    ]
                     with m.If(~wb.stall):
                         m.next = "READACK"
                 with m.State("READACK"):
-                    m.d.comb += [
-                        wb.cyc.eq(1),
-                        wb.stb.eq(0),
-                        wb.we.eq(0),
-                    ]
                     with m.If(wb.ack):
                         # Store read data in sr_data.i and keep it there til next read
                         m.d[domain] += sr_data.i.eq(wb.dat_r)
                         m.next = "IDLE"
                 with m.State("WRITEREAD"):
-                    m.d.comb += [
-                        wb.cyc.eq(1),
-                        wb.stb.eq(1),
-                        wb.we.eq(1),
-                    ]
                     with m.If(~wb.stall):
                         m.next = "WRITEREADACK"
                 with m.State("WRITEREADACK"):
-                    m.d.comb += [
-                        wb.cyc.eq(1),
-                        wb.stb.eq(0),
-                        wb.we.eq(0),
-                    ]
                     with m.If(wb.ack):
                         m.d[domain] += wb.adr.eq(wb.adr + 1)
                         m.next = "READ"
+
+                m.d.comb += [
+                    wb.cyc.eq(~fsm.ongoing("IDLE")),
+                    wb.stb.eq(fsm.ongoing("READ") | fsm.ongoing("WRITEREAD")),
+                    wb.we.eq(fsm.ongoing("WRITEREAD")),
+                ]
-- 
2.30.2