From 2a79bc6819881b5caf8084f89cf76b56f36627b0 Mon Sep 17 00:00:00 2001
From: David Banks <dave@hoglet.com>
Date: Tue, 1 Oct 2019 15:21:28 +0100
Subject: [PATCH] 6809: Added special command to inhibit IRQ/FIRQ/NMI

Change-Id: I9b94fec5f464ecdb6bb0a4cd2a430401a182c929
---
 firmware/AtomBusMon.c |  8 ++++----
 src/MC6809ECpuMon.vhd | 16 +++++++++++++---
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/firmware/AtomBusMon.c b/firmware/AtomBusMon.c
index 7e3e175..b939f38 100644
--- a/firmware/AtomBusMon.c
+++ b/firmware/AtomBusMon.c
@@ -10,7 +10,7 @@
  * VERSION and NAME are used in the start-up message
  ********************************************************/
 
-#define VERSION "0.75"
+#define VERSION "0.76"
 
 #if (CPU == Z80)
   #define NAME "ICE-T80"
@@ -51,7 +51,7 @@ char *cmdStrings[] = {
 #endif
   "test",
   "srec",
-#if (CPU == 6502)
+#if (CPU != Z80)
   "special",
 #endif
 #endif
@@ -94,7 +94,7 @@ void (*cmdFuncs[])(char *params) = {
 #endif
   doCmdTest,
   doCmdSRec,
-#if (CPU == 6502)
+#if (CPU != Z80)
   doCmdSpecial,
 #endif
 #endif
@@ -1160,7 +1160,7 @@ void doCmdSRec(char *params) {
 
 }
 
-#if (CPU == 6502)
+#if (CPU != Z80)
 void logSpecial(char *function, int value) {
    log0("%s", function);
    if (value) {
diff --git a/src/MC6809ECpuMon.vhd b/src/MC6809ECpuMon.vhd
index d0a6c90..37ffbc4 100644
--- a/src/MC6809ECpuMon.vhd
+++ b/src/MC6809ECpuMon.vhd
@@ -132,6 +132,7 @@ architecture behavioral of MC6809ECpuMon is
     signal SS_Single      : std_logic;
     signal SS_Step        : std_logic;
     signal CountCycle     : std_logic;
+    signal special       : std_logic_vector(1 downto 0);
 
     signal clk_count      : std_logic_vector(1 downto 0);
     signal quadrature     : std_logic_vector(1 downto 0);
@@ -166,6 +167,10 @@ architecture behavioral of MC6809ECpuMon is
     signal sw_interrupt_n : std_logic;  -- switch to pause the CPU
     signal sw_reset_n     : std_logic;  -- switch to reset the CPU
 
+    signal NMI_n_masked   : std_logic;
+    signal IRQ_n_masked   : std_logic;
+    signal FIRQ_n_masked  : std_logic;
+
 begin
 
     -- Generics allows polarity of switches/LEDs to be tweaked from the project file
@@ -232,10 +237,15 @@ begin
         DataOut      => memory_dout,
         DataIn       => memory_din,
         Done         => memory_done,
+        Special      => special,
         SS_Step      => SS_Step,
         SS_Single    => SS_Single
     );
 
+    NMI_n_masked  <= NMI_n  or special(1);
+    FIRQ_n_masked <= FIRQ_n or special(1);
+    IRQ_n_masked  <= IRQ_n  or special(0);
+
     -- The CPU is slightly pipelined and the register update of the last
     -- instruction overlaps with the opcode fetch of the next instruction.
     --
@@ -290,9 +300,9 @@ begin
     irq_gen : process(cpu_clk)
     begin
         if falling_edge(cpu_clk) then
-            NMI_sync   <= not NMI_n;
-            IRQ_sync   <= not IRQ_n;
-            FIRQ_sync  <= not FIRQ_n;
+            NMI_sync   <= not NMI_n_masked;
+            IRQ_sync   <= not IRQ_n_masked;
+            FIRQ_sync  <= not FIRQ_n_masked;
             nRST_sync  <= RES_n and nRSTout;
             HALT_sync  <= not HALT_n;
         end if;