diff --git a/src/devices/cpu/sm510/sm510.cpp b/src/devices/cpu/sm510/sm510.cpp
index ab1b4cb0ebb..69a099f1cb4 100644
--- a/src/devices/cpu/sm510/sm510.cpp
+++ b/src/devices/cpu/sm510/sm510.cpp
@@ -68,6 +68,37 @@ void sm510_base_device::device_start()
 	m_write_segbs.resolve_safe();
 	m_write_segc.resolve_safe();
 
+	// zerofill
+	memset(m_stack, 0, sizeof(m_stack));
+	m_pc = 0;
+	m_prev_pc = 0;
+	m_op = 0;
+	m_prev_op = 0;
+	m_param = 0;
+	m_acc = 0;
+	m_bl = 0;
+	m_bm = 0;
+	m_sbm = false;
+	m_c = 0;
+	m_skip = false;
+	m_w = 0;
+	m_r = 0;
+	m_r_out = 0;
+	m_div = 0;
+	m_1s = false;
+	m_k_active = false;
+	m_l = 0;
+	m_x = 0;
+	m_y = 0;
+	m_bp = false;
+	m_bc = false;
+	m_halt = false;
+	m_melody_rd = 0;
+	m_melody_step_count = 0;
+	m_melody_duty_count = 0;
+	m_melody_duty_index = 0;
+	m_melody_address = 0;
+
 	// register for savestates
 	save_item(NAME(m_stack));
 	save_item(NAME(m_pc));
@@ -78,10 +109,12 @@ void sm510_base_device::device_start()
 	save_item(NAME(m_acc));
 	save_item(NAME(m_bl));
 	save_item(NAME(m_bm));
+	save_item(NAME(m_sbm));
 	save_item(NAME(m_c));
 	save_item(NAME(m_skip));
 	save_item(NAME(m_w));
 	save_item(NAME(m_r));
+	save_item(NAME(m_r_out));
 	save_item(NAME(m_div));
 	save_item(NAME(m_1s));
 	save_item(NAME(m_k_active));
@@ -138,7 +171,7 @@ void sm510_base_device::device_reset()
 	m_bc = false;
 	m_y = 0;
 
-	m_r = 0;
+	m_r = m_r_out = 0;
 	m_write_r(0, 0, 0xff);
 	m_melody_rd &= ~1;
 }
@@ -190,82 +223,6 @@ void sm510_base_device::init_lcd_driver()
 
 
 
-//-------------------------------------------------
-//  melody controller
-//-------------------------------------------------
-
-void sm510_base_device::clock_melody()
-{
-	if (!m_melody_rom)
-		return;
-
-	// tone cycle table (SM511/SM512 datasheet fig.5)
-	// cmd 0 = cmd, 1 = stop, > 13 = illegal(unknown)
-	static const u8 lut_tone_cycles[4*16] =
-	{
-		0, 0, 7, 8, 8, 9, 9, 10,11,11,12,13,14,14, 7*2, 8*2,
-		0, 0, 8, 8, 9, 9, 10,11,11,12,13,13,14,15, 8*2, 8*2,
-		0, 0, 8, 8, 9, 9, 10,10,11,12,12,13,14,15, 8*2, 8*2,
-		0, 0, 8, 9, 9, 10,10,11,11,12,13,14,14,15, 8*2, 9*2
-	};
-
-	u8 cmd = m_melody_rom[m_melody_address] & 0x3f;
-	u8 out = 0;
-
-	// clock duty cycle if tone is active
-	if ((cmd & 0xf) > 1)
-	{
-		out = m_melody_duty_index & m_melody_rd & 1;
-		m_melody_duty_count++;
-		int index = m_melody_duty_index << 4 | (cmd & 0xf);
-		int shift = ~cmd >> 4 & 1; // OCT
-
-		if (m_melody_duty_count >= (lut_tone_cycles[index] << shift))
-		{
-			m_melody_duty_count = 0;
-			m_melody_duty_index = (m_melody_duty_index + 1) & 3;
-		}
-	}
-	else if ((cmd & 0xf) == 1)
-	{
-		// rest tell signal
-		m_melody_rd |= 2;
-	}
-
-	// clock time base on F8(d7)
-	if ((m_div & 0x7f) == 0)
-	{
-		u8 mask = (cmd & 0x20) ? 0x1f : 0x0f;
-		m_melody_step_count = (m_melody_step_count + 1) & mask;
-
-		if (m_melody_step_count == 0)
-			m_melody_address++;
-	}
-
-	// output to R pin
-	if (out != m_r)
-	{
-		m_write_r(0, out, 0xff);
-		m_r = out;
-	}
-}
-
-void sm510_base_device::init_melody()
-{
-	if (!m_melody_rom)
-		return;
-
-	// verify melody rom
-	for (int i = 0; i < 0x100; i++)
-	{
-		u8 data = m_melody_rom[i];
-		if (data & 0xc0 || (data & 0x0f) > 13)
-			logerror("%s unknown melody ROM data $%02X at $%02X\n", tag(), data, i);
-	}
-}
-
-
-
 //-------------------------------------------------
 //  interrupt/divider
 //-------------------------------------------------
diff --git a/src/devices/cpu/sm510/sm510.h b/src/devices/cpu/sm510/sm510.h
index 68f8f780fa9..b0dd41e408f 100644
--- a/src/devices/cpu/sm510/sm510.h
+++ b/src/devices/cpu/sm510/sm510.h
@@ -174,7 +174,7 @@ protected:
 	u8 m_c;
 	bool m_skip;
 	u8 m_w;
-	u8 m_r;
+	u8 m_r, m_r_out;
 	bool m_k_active;
 	bool m_halt;
 
@@ -199,8 +199,8 @@ protected:
 	u8 m_melody_duty_index;
 	u8 m_melody_address;
 
-	void clock_melody();
-	void init_melody();
+	virtual void clock_melody() { }
+	virtual void init_melody() { }
 
 	// interrupt/divider
 	emu_timer *m_div_timer;
@@ -311,6 +311,8 @@ protected:
 	virtual void get_opcode_param() override;
 
 	virtual void update_w_latch() override { m_write_s(0, m_w, 0xff); } // W is connected directly to S
+
+	virtual void clock_melody() override;
 };
 
 
@@ -324,6 +326,9 @@ protected:
 	virtual offs_t disasm_disassemble(std::ostream &stream, offs_t pc, const u8 *oprom, const u8 *opram, u32 options) override;
 	virtual void execute_one() override;
 	virtual void get_opcode_param() override;
+
+	virtual void clock_melody() override;
+	virtual void init_melody() override;
 };
 
 class sm512_device : public sm511_device
diff --git a/src/devices/cpu/sm510/sm510core.cpp b/src/devices/cpu/sm510/sm510core.cpp
index a531fc37e69..c739fa83ffe 100644
--- a/src/devices/cpu/sm510/sm510core.cpp
+++ b/src/devices/cpu/sm510/sm510core.cpp
@@ -45,6 +45,27 @@ offs_t sm510_device::disasm_disassemble(std::ostream &stream, offs_t pc, const u
 
 
 
+//-------------------------------------------------
+//  buzzer controller
+//-------------------------------------------------
+
+void sm510_device::clock_melody()
+{
+	// buzzer from divider, R2 inverse phase
+	u8 out = m_div >> 2 & 1;
+	out |= (out << 1 ^ 2);
+	out &= m_r;
+	
+	// output to R pin
+	if (out != m_r_out)
+	{
+		m_write_r(0, out, 0xff);
+		m_r_out = out;
+	}
+}
+
+
+
 //-------------------------------------------------
 //  execute
 //-------------------------------------------------
diff --git a/src/devices/cpu/sm510/sm510op.cpp b/src/devices/cpu/sm510/sm510op.cpp
index f0a32851708..8b248c2cf90 100644
--- a/src/devices/cpu/sm510/sm510op.cpp
+++ b/src/devices/cpu/sm510/sm510op.cpp
@@ -263,11 +263,7 @@ void sm510_base_device::op_atfc()
 void sm510_base_device::op_atr()
 {
 	// ATR: output ACC to R
-	if (m_r != (m_acc & 3))
-	{
-		m_r = m_acc & 3;
-		m_write_r(0, m_r, 0xff);
-	}
+	m_r = m_acc;
 }
 
 
diff --git a/src/devices/cpu/sm510/sm511core.cpp b/src/devices/cpu/sm510/sm511core.cpp
index 1c40e781764..54f9db77e84 100644
--- a/src/devices/cpu/sm510/sm511core.cpp
+++ b/src/devices/cpu/sm510/sm511core.cpp
@@ -58,6 +58,82 @@ sm512_device::sm512_device(const machine_config &mconfig, const char *tag, devic
 
 
 
+//-------------------------------------------------
+//  melody controller
+//-------------------------------------------------
+
+void sm511_device::clock_melody()
+{
+	if (!m_melody_rom)
+		return;
+
+	// tone cycle table (SM511/SM512 datasheet fig.5)
+	// cmd 0 = cmd, 1 = stop, > 13 = illegal(unknown)
+	static const u8 lut_tone_cycles[4*16] =
+	{
+		0, 0, 7, 8, 8, 9, 9, 10,11,11,12,13,14,14, 7*2, 8*2,
+		0, 0, 8, 8, 9, 9, 10,11,11,12,13,13,14,15, 8*2, 8*2,
+		0, 0, 8, 8, 9, 9, 10,10,11,12,12,13,14,15, 8*2, 8*2,
+		0, 0, 8, 9, 9, 10,10,11,11,12,13,14,14,15, 8*2, 9*2
+	};
+
+	u8 cmd = m_melody_rom[m_melody_address] & 0x3f;
+	u8 out = 0;
+
+	// clock duty cycle if tone is active
+	if ((cmd & 0xf) > 1)
+	{
+		out = m_melody_duty_index & m_melody_rd & 1;
+		m_melody_duty_count++;
+		int index = m_melody_duty_index << 4 | (cmd & 0xf);
+		int shift = ~cmd >> 4 & 1; // OCT
+
+		if (m_melody_duty_count >= (lut_tone_cycles[index] << shift))
+		{
+			m_melody_duty_count = 0;
+			m_melody_duty_index = (m_melody_duty_index + 1) & 3;
+		}
+	}
+	else if ((cmd & 0xf) == 1)
+	{
+		// rest tell signal
+		m_melody_rd |= 2;
+	}
+
+	// clock time base on F8(d7)
+	if ((m_div & 0x7f) == 0)
+	{
+		u8 mask = (cmd & 0x20) ? 0x1f : 0x0f;
+		m_melody_step_count = (m_melody_step_count + 1) & mask;
+
+		if (m_melody_step_count == 0)
+			m_melody_address++;
+	}
+
+	// output to R pin
+	if (out != m_r_out)
+	{
+		m_write_r(0, out, 0xff);
+		m_r_out = out;
+	}
+}
+
+void sm511_device::init_melody()
+{
+	if (!m_melody_rom)
+		return;
+
+	// verify melody rom
+	for (int i = 0; i < 0x100; i++)
+	{
+		u8 data = m_melody_rom[i];
+		if (data & 0xc0 || (data & 0x0f) > 13)
+			logerror("%s unknown melody ROM data $%02X at $%02X\n", tag(), data, i);
+	}
+}
+
+
+
 //-------------------------------------------------
 //  execute
 //-------------------------------------------------