diff --git a/dsim.c b/dsim.c
index f58bf72..95a037a 100644
--- a/dsim.c
+++ b/dsim.c
@@ -19,6 +19,7 @@ uint16_t lit; /* temporary storage for literal operands */
 bool skip_next;
 uint64_t ticks;
 bool running;
+bool trace;
 bool intq_en;
 #define MAX_INTQ_SIZE 256
 uint16_t intq[MAX_INTQ_SIZE];
@@ -75,6 +76,7 @@ void reset()
     skip_next = false;
     ticks = 0;
 
+    trace = false;
     running = true;
 }
 
@@ -100,6 +102,12 @@ void debug_irqh()
     case 0x0002:
         dump_ram(ry, rx);
         break;
+    case 0x0004:
+        trace = false;
+        break;
+    case 0x0005:
+        trace = true;
+        break;
     case 0xffff:
         rx = EMU_ID;
         ry = EMU_VER;
@@ -496,6 +504,9 @@ void next()
         }
     }
 
+    if (trace)
+        dumpregs();
+
     ir = ram[rpc++];
 
     opcode = ir & 0x001f;