Z80 daisy chain stuff

- Reconfigure Z80 daisy chain behavior to use the standard vector for an external IRQ, rather than a bogus one from the last device in the chain
- Enable Z80 daisy chain on Cedar Magnet sound board (fake IRQ still necessary, though vectors are correct now)
- Source note regarding IM 2 behavior contrary to Zilog datasheet (nw; was fixed way back in 0.35b11)

src/devices/cpu/z180/z180.cpp

@@ -1969,6 +1969,8 @@ void z180_device::device_start()
 	m_odirect = &m_oprogram->direct();
 	m_iospace = &space(AS_IO);
 
+	daisy_set_irq_callback(device_irq_acknowledge_delegate(FUNC(z180_device::standard_irq_callback_member), this));
+
 	/* set up the state table */
 	{
 		state_add(Z180_PC,         "PC",        m_PC.w.l);

src/devices/cpu/z180/z180op.hxx

@@ -306,13 +306,8 @@ int z180_device::take_interrupt(int irq)
 
 	if( irq == Z180_INT_IRQ0 )
 	{
-		/* Daisy chain mode? If so, call the requesting device */
-		if (daisy_chain_present())
-			irq_vector = daisy_call_ack_device();
-
-		/* else call back the cpu interface to retrieve the vector */
-		else
-			irq_vector = standard_irq_callback(0);
+		// retrieve the IRQ vector from the daisy chain or CPU interface
+		irq_vector = daisy_call_ack_device();
 
 		LOG(("Z180 '%s' single int. irq_vector $%02x\n", tag(), irq_vector));
 

src/devices/cpu/z80/z80.cpp

@@ -3146,32 +3146,27 @@ void z80_device::take_nmi()
 
 void z80_device::take_interrupt()
 {
-	int irq_vector;
-
 	PRVPC = 0xffff; // HACK: segag80r protection kludge
 
-	/* Check if processor was halted */
+	// check if processor was halted
 	leave_halt();
 
-	/* Clear both interrupt flip flops */
+	// clear both interrupt flip flops
 	m_iff1 = m_iff2 = 0;
 
-	/* Daisy chain mode? If so, call the requesting device */
-	if (daisy_chain_present())
-		irq_vector = daisy_call_ack_device();
-
-	/* else call back the cpu interface to retrieve the vector */
-	else
-		irq_vector = m_irq_callback(*this, 0);
-
-	/* Say hi */
+	// say hi
 	m_irqack_cb(true);
 
+	// fetch the IRQ vector
+	int irq_vector = daisy_call_ack_device();
 	LOG(("Z80 '%s' single int. irq_vector $%02x\n", tag(), irq_vector));
 
 	/* Interrupt mode 2. Call [i:databyte] */
 	if( m_im == 2 )
 	{
+		// Zilog's datasheet claims that "the least-significant bit must be a zero."
+		// However, experiments have confirmed that IM 2 vectors do not have to be
+		// even, and all 8 bits will be used; even $FF is handled normally.
 		irq_vector = (irq_vector & 0xff) | (m_i << 8);
 		push(m_pc);
 		rm16(irq_vector, m_pc);
@@ -3415,7 +3410,7 @@ void z80_device::device_start()
 	m_decrypted_opcodes_direct = &m_decrypted_opcodes->direct();
 	m_io = &space(AS_IO);
 
-	m_irq_callback = device_irq_acknowledge_delegate(FUNC(z80_device::standard_irq_callback_member), this);
+	daisy_set_irq_callback(device_irq_acknowledge_delegate(FUNC(z80_device::standard_irq_callback_member), this));
 
 	IX = IY = 0xffff; /* IX and IY are FFFF after a reset! */
 	F = ZF;            /* Zero flag is set */

src/devices/cpu/z80/z80.h

@@ -276,7 +276,6 @@ protected:
 	uint8_t           m_after_ei;           /* are we in the EI shadow? */
 	uint8_t           m_after_ldair;        /* same, but for LD A,I or LD A,R */
 	uint32_t          m_ea;
-	device_irq_acknowledge_delegate m_irq_callback;
 
 	int             m_icount;
 	uint8_t           m_rtemp;

src/devices/cpu/z80/z80daisy.cpp

@@ -11,6 +11,8 @@
 #include "emu.h"
 #include "z80daisy.h"
 
+#define VERBOSE 0
+
 
 //**************************************************************************
 //  DEVICE Z80 DAISY INTERFACE
@@ -170,19 +172,20 @@ int z80_daisy_chain_interface::daisy_update_irq_state()
 
 int z80_daisy_chain_interface::daisy_call_ack_device()
 {
-	int vector = 0;
-
 	// loop over all devices; dev[0] is the highest priority
 	for (device_z80daisy_interface *intf = m_chain; intf != nullptr; intf = intf->m_daisy_next)
 	{
 		// if this device is asserting the INT line, that's the one we want
 		int state = intf->z80daisy_irq_state();
-		vector = intf->z80daisy_irq_ack();
 		if (state & Z80_DAISY_INT)
-			return vector;
+			return intf->z80daisy_irq_ack(); // call the requesting device
 	}
-	//logerror("z80daisy_call_ack_device: failed to find an device to ack!\n");
-	return vector;
+
+	if (VERBOSE && daisy_chain_present())
+		device().logerror("Interrupt from outside Z80 daisy chain\n");
+
+	// call back the CPU interface to retrieve the vector
+	return m_irq_callback(device(), 0);
 }
 
 
@@ -204,7 +207,6 @@ void z80_daisy_chain_interface::daisy_call_reti_device()
 			return;
 		}
 	}
-	//logerror("z80daisy_call_reti_device: failed to find an device to reti!\n");
 }
 
 

src/devices/cpu/z80/z80daisy.h

@@ -94,6 +94,7 @@ protected:
 
 	// initialization
 	void daisy_init(const z80_daisy_config *daisy);
+	void daisy_set_irq_callback(const device_irq_acknowledge_delegate &callback) { m_irq_callback = callback; }
 
 	// callbacks
 	int daisy_update_irq_state();
@@ -103,6 +104,7 @@ protected:
 private:
 	const z80_daisy_config *m_daisy_config;
 	device_z80daisy_interface *m_chain;     // head of the daisy chain
+	device_irq_acknowledge_delegate m_irq_callback;
 };
 
 

src/mame/machine/cedar_magnet_sound.cpp

@@ -10,20 +10,16 @@
 
    0xe6 - from ctc0 channel 3 (vector = E0) used to drive MSM5205 through FIFO
    0xee - from ctc0 channel 3 (vector = E8) ^^
-   0xf6 - drive AY (once per frame?) triggered by ctc1 channel 3? (sets vector to f0, f6 = channel3?)
-   0xff - read sound latch (triggered by write from master board)
-
-   any attempts made to hook up the ctcs end up resulting in it taking an interrupt
-   with vector 0xf0, which points to 0x0000 and resets the cpu?!
-
-   does the device here also need to add daisychain functions in order for the 0xff vector to be used
-   with the soundlatch writes?
+   0xf6 - drive AY (once per frame?) triggered by ctc1 channel 3 (vector = F0)
+   0xff - read sound latch (triggered by write from master board; default vector set by 5K/+5 pullups on D0-D7)
 
 */
 
 #include "emu.h"
 #include "cedar_magnet_sound.h"
 
+#include "machine/clock.h"
+
 
 extern const device_type CEDAR_MAGNET_SOUND = &device_creator<cedar_magnet_sound_device>;
 
@@ -47,7 +43,7 @@ void cedar_magnet_sound_device::write_command(uint8_t data)
 {
 	m_command = data;
 	// this interrupt causes it to read the soundlatch at 0x14
-	m_cpu->set_input_line_and_vector(0, HOLD_LINE,0xff);
+	m_cpu->set_input_line_and_vector(0, HOLD_LINE, 0xff);
 }
 
 
@@ -58,6 +54,7 @@ ADDRESS_MAP_END
 
 static ADDRESS_MAP_START( cedar_magnet_sound_io, AS_IO, 8, cedar_magnet_sound_device )
 	ADDRESS_MAP_GLOBAL_MASK(0xff)
+	ADDRESS_MAP_UNMAP_HIGH
 
 	AM_RANGE(0x00, 0x03) AM_DEVREADWRITE("ctc0", z80ctc_device, read, write)
 	AM_RANGE(0x04, 0x07) AM_DEVREADWRITE("ctc1", z80ctc_device, read, write)
@@ -133,15 +130,12 @@ WRITE_LINE_MEMBER(cedar_magnet_sound_device::fifo_dor_w)
 	// combined with a clock signal and used to drive ctc0 channel 3
 }
 
-#if 0
 static const z80_daisy_config daisy_chain[] =
 {
 	{ "ctc1" },
 	{ "ctc0" },
-// soundlatch from main CPU needs to be able to generate a vector too?
 	{ nullptr }
 };
-#endif
 
 TIMER_CALLBACK_MEMBER(cedar_magnet_sound_device::reset_assert_callback)
 {
@@ -169,7 +163,7 @@ static MACHINE_CONFIG_FRAGMENT( cedar_magnet_sound )
 	MCFG_CPU_ADD("topcpu", Z80, 4000000)
 	MCFG_CPU_PROGRAM_MAP(cedar_magnet_sound_map)
 	MCFG_CPU_IO_MAP(cedar_magnet_sound_io)
-//  MCFG_Z80_DAISY_CHAIN(daisy_chain)
+	MCFG_Z80_DAISY_CHAIN(daisy_chain)
 	MCFG_CPU_PERIODIC_INT_DRIVER(cedar_magnet_sound_device, fake_irq, 4*60)
 
 	MCFG_DEVICE_ADD("ctc0", Z80CTC, 4000000)
@@ -184,6 +178,13 @@ static MACHINE_CONFIG_FRAGMENT( cedar_magnet_sound )
 	MCFG_Z80CTC_ZC1_CB(WRITELINE(cedar_magnet_sound_device, ctc1_z1_w))
 	MCFG_Z80CTC_ZC2_CB(WRITELINE(cedar_magnet_sound_device, ctc1_z2_w))
 
+#if 0 // does nothing useful now
+	MCFG_DEVICE_ADD("ck1mhz", CLOCK, 4000000/4)
+	MCFG_CLOCK_SIGNAL_HANDLER(DEVWRITELINE("ctc1", z80ctc_device, trg0))
+	MCFG_DEVCB_CHAIN_OUTPUT(DEVWRITELINE("ctc1", z80ctc_device, trg1))
+	MCFG_DEVCB_CHAIN_OUTPUT(DEVWRITELINE("ctc1", z80ctc_device, trg2))
+#endif
+
 	MCFG_SPEAKER_STANDARD_MONO("mono")
 
 	MCFG_SOUND_ADD("aysnd0", AY8910, 4000000/2)