Critical fixes (nw)

- Prevent tmpz84c015_device::irq_priority_w from crashing or corrupting the daisy chain
- Eliminate the need for TMPZ84C015_DAISY_INTERNAL by not overwriting elements in the daisy list
- Removed leftover MCFG_SEGAZ80_SET_DECRYPTED_TAG from macros in system1.cpp, which lets all drivers validate without crashing

src/devices/cpu/z80/tmpz84c015.cpp

@@ -155,7 +155,7 @@ WRITE8_MEMBER(tmpz84c015_device::irq_priority_w)
 			{ 1, 2, 0 }  // 5: sio -> pio -> ctc -> ext
 		};
 
-		// reconfigure first 3 entries in daisy chain
+		// reconfigure daisy chain
 		const z80_daisy_config daisy_chain[] =
 		{
 			{ dev[prio[data][0]] },
@@ -163,6 +163,8 @@ WRITE8_MEMBER(tmpz84c015_device::irq_priority_w)
 			{ dev[prio[data][2]] },
 			{ nullptr }
 		};
+
+		// insert these 3 entries in order before any externally linked devices
 		daisy_init(daisy_chain);
 
 		m_irq_priority = data;

src/devices/cpu/z80/tmpz84c015.h

@@ -23,9 +23,6 @@
     DEVICE CONFIGURATION MACROS
 ***************************************************************************/
 
-// If an external daisy chain is used, insert this before your own device tags:
-#define TMPZ84C015_DAISY_INTERNAL { "tmpz84c015_ctc" }, { "tmpz84c015_sio" }, { "tmpz84c015_pio" }
-
 // SIO callbacks
 #define MCFG_TMPZ84C015_OUT_TXDA_CB(_devcb) \
 	devcb = &tmpz84c015_device::set_out_txda_callback(*device, DEVCB_##_devcb);

src/devices/cpu/z80/z80daisy.cpp

@@ -87,6 +87,8 @@ void z80_daisy_chain_interface::interface_post_start()
 
 void z80_daisy_chain_interface::daisy_init(const z80_daisy_config *daisy)
 {
+	assert(daisy != nullptr);
+
 	// create a linked list of devices
 	device_z80daisy_interface **tailptr = &m_chain;
 	for ( ; daisy->devname != nullptr; daisy++)
@@ -105,12 +107,23 @@ void z80_daisy_chain_interface::daisy_init(const z80_daisy_config *daisy)
 		if (!target->interface(intf))
 			fatalerror("Device '%s' does not implement the z80daisy interface!\n", daisy->devname);
 
-		// append to the end, or overwrite existing entry
+		// splice it out of the list if it was previously added
-		device_z80daisy_interface *next = (*tailptr != nullptr) ? (*tailptr)->m_daisy_next : nullptr;
+		device_z80daisy_interface **oldtailptr = tailptr;
+		while (*oldtailptr != nullptr)
+		{
+			if (*oldtailptr == intf)
+				*oldtailptr = (*oldtailptr)->m_daisy_next;
+			else
+				oldtailptr = &(*oldtailptr)->m_daisy_next;
+		}
+
+		// add the interface to the list
+		intf->m_daisy_next = *tailptr;
 		*tailptr = intf;
-		(*tailptr)->m_daisy_next = next;
 		tailptr = &(*tailptr)->m_daisy_next;
 	}
+
+	osd_printf_verbose("Daisy chain = %s\n", daisy_show_chain().c_str());
 }
 
 
@@ -193,3 +206,24 @@ void z80_daisy_chain_interface::daisy_call_reti_device()
 	}
 	//logerror("z80daisy_call_reti_device: failed to find an device to reti!\n");
 }
+
+
+//-------------------------------------------------
+//  daisy_show_chain - list devices in the chain
+//  in string format (for debugging purposes)
+//-------------------------------------------------
+
+std::string z80_daisy_chain_interface::daisy_show_chain() const
+{
+	std::ostringstream result;
+
+	// loop over all devices
+	for (device_z80daisy_interface *intf = m_chain; intf != nullptr; intf = intf->m_daisy_next)
+	{
+		if (intf != m_chain)
+			result << " -> ";
+		result << intf->device().tag();
+	}
+
+	return result.str();
+}

src/devices/cpu/z80/z80daisy.h

@@ -85,6 +85,7 @@ public:
 
 	// getters
 	bool daisy_chain_present() const { return (m_chain != nullptr); }
+	std::string daisy_show_chain() const;
 
 protected:
 	// interface-level overrides

src/mame/drivers/pve500.cpp

@@ -102,7 +102,6 @@ WRITE_LINE_MEMBER( pve500_state::external_monitor_w )
 
 static const z80_daisy_config maincpu_daisy_chain[] =
 {
-	TMPZ84C015_DAISY_INTERNAL,
 	{ "external_ctc" },
 	{ "external_sio" },
 	{ nullptr }

src/mame/drivers/system1.cpp

@@ -2222,15 +2222,13 @@ MACHINE_CONFIG_END
 	MCFG_CPU_PROGRAM_MAP(system1_map) \
 	MCFG_CPU_DECRYPTED_OPCODES_MAP(decrypted_opcodes_map) \
 	MCFG_CPU_IO_MAP(system1_ppi_io_map) \
-	MCFG_CPU_VBLANK_INT_DRIVER("screen", system1_state, irq0_line_hold) \
+	MCFG_CPU_VBLANK_INT_DRIVER("screen", system1_state, irq0_line_hold)
-	MCFG_SEGAZ80_SET_DECRYPTED_TAG(":decrypted_opcodes")
 
 #define ENCRYPTED_SYS1PIO_MAPS \
 	MCFG_CPU_PROGRAM_MAP(system1_map) \
 	MCFG_CPU_DECRYPTED_OPCODES_MAP(decrypted_opcodes_map) \
 	MCFG_CPU_IO_MAP(system1_pio_io_map) \
-	MCFG_CPU_VBLANK_INT_DRIVER("screen", system1_state, irq0_line_hold) \
+	MCFG_CPU_VBLANK_INT_DRIVER("screen", system1_state, irq0_line_hold)
-	MCFG_SEGAZ80_SET_DECRYPTED_TAG(":decrypted_opcodes")
 
 
 static MACHINE_CONFIG_DERIVED( sys1ppix_315_5178, sys1ppi )