diff --git a/bus.cpp b/bus.cpp
index e196b5f..5b90ac8 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -64,7 +64,8 @@ uint16_t bus::read(const uint16_t a, const bool word_mode, const bool use_prev,
 
 		if (a == 0177570) { // console switch & display register
 			D(fprintf(stderr, "read console switch\n");)
-			return 128; // educated guess
+
+			return debug_mode ? 128 : 0;
 		}
 
 		if (a == 0172540) { // KW11P programmable clock
diff --git a/bus.h b/bus.h
index 077ded7..6d9a52a 100644
--- a/bus.h
+++ b/bus.h
@@ -21,27 +21,31 @@ typedef struct
 class bus
 {
 private:
-	cpu    *c     { nullptr };
-	tm_11  *tm11  { nullptr };
-	rk05   *rk05_ { nullptr };
-	rx02   *rx02_ { nullptr };
-	tty    *tty_  { nullptr };
+	cpu     *c     { nullptr };
+	tm_11   *tm11  { nullptr };
+	rk05    *rk05_ { nullptr };
+	rx02    *rx02_ { nullptr };
+	tty     *tty_  { nullptr };
 
-	memory *m     { nullptr };
+	memory  *m     { nullptr };
 
 	// 8 pages, D/I, 3 modes and 1 invalid mode
-	page_t  pages[4][2][8];
+	page_t   pages[4][2][8];
 
 	uint16_t MMR0 { 0 }, MMR1 { 0 }, MMR2 { 0 }, MMR3 { 0 }, CPUERR { 0 }, PIR { 0 }, CSR { 0 };
 
 	uint16_t switch_register { 0 };
 
+	bool     debug_mode { false };
+
 public:
 	bus();
 	~bus();
 
 	void clearmem();
 
+	void set_debug_mode(const bool state) { debug_mode = state; }
+
 	void add_cpu(cpu *const c) { this -> c = c; }
 	void add_tm11(tm_11 *tm11) { this -> tm11 = tm11; } 
 	void add_rk05(rk05 *rk05_) { this -> rk05_ = rk05_; } 
diff --git a/debugger.cpp b/debugger.cpp
index 0d68643..ddefb13 100644
--- a/debugger.cpp
+++ b/debugger.cpp
@@ -76,6 +76,8 @@ void debugger(console *const cnsl, bus *const b, std::atomic_bool *const interru
 {
 	cpu *const c = b->getCpu();
 
+	b->set_debug_mode(true);
+
 	bool single_step = false;
 
 	while(!terminate) {