From 441fe12b0acee6cf053c2a10df578be10723c52a Mon Sep 17 00:00:00 2001
From: Warren Toomey <wkt@tuhs.org>
Date: Thu, 24 Mar 2016 08:57:51 +1000
Subject: [PATCH] Fall into single-step mode if we see a low memory write.

---
 tools/a7out | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/a7out b/tools/a7out
index 54ddec4..246e817 100755
--- a/tools/a7out
+++ b/tools/a7out
@@ -354,7 +354,13 @@ sub lac {
 sub dac {
     my ( $instruction, $addr, $indaddr ) = @_;
     dprintf( "dac AC (value %06o) into %s\n", $AC, addr($indaddr) );
-    dprintf("(****WRITE TO LOW MEMORY****)\n") if ($indaddr < 010000 && !($indaddr >= 010 && $indaddr <= 020) ) ;
+
+    # Catch writes below the process' memory range
+    if ($indaddr < 010000 && !($indaddr >= 010 && $indaddr <= 020) ) {
+      $singlestep = 1;
+      dprintf("(****WRITE TO LOW MEMORY****)\n");
+      dprintf( "break at PC %s\n", addr($PC) );
+    }
     $Mem[$indaddr] = $AC;
     $PC++;
 }