wd_fdc: Add a MON callback so that drives, which are unselected early, do not spin forever.

src/devices/bus/ti99/peb/myarcfdc.cpp

@@ -16,8 +16,6 @@
     Another switch is included (SW2) labeled "Turbo" on schematics, but which
     is not present on all boards. It may require a different ROM.
 
-    Known issue: On error, the drive may continue spinning.
-    
     Michael Zapf
     March 2020
 
@@ -255,6 +253,17 @@ WRITE_LINE_MEMBER( myarc_fdc_device::fdc_drq_w )
 	LOGMASKED(LOG_DRQ, "DRQ callback = %d\n", state);
 }
 
+WRITE_LINE_MEMBER( myarc_fdc_device::fdc_mon_w )
+{
+	LOGMASKED(LOG_DRIVE, "MON callback = %d\n", state);
+	// All MON lines are connected
+	// Do not start the motors when no drive is selected. However, motors
+	// can always be stopped.
+	if (m_selected_drive != 0 || state==1)
+		for (int i=0; i < 3; i++)
+			if (m_floppy[i] != nullptr) m_floppy[i]->mon_w(state);
+}
+
 /*
     Callbacks from the 74LS259 latch
 */
@@ -322,7 +331,6 @@ WRITE_LINE_MEMBER( myarc_fdc_device::drivesel_w )
 	}
 }
 
-
 void myarc_fdc_device::device_start()
 {
 	m_dsrrom = memregion(TI99_DSRROM)->base();
@@ -403,8 +411,13 @@ void myarc_fdc_device::device_add_mconfig(machine_config& config)
 
 	m_wd1770->intrq_wr_callback().set(FUNC(myarc_fdc_device::fdc_irq_w));
 	m_wd1770->drq_wr_callback().set(FUNC(myarc_fdc_device::fdc_drq_w));
+	m_wd1770->mon_wr_callback().set(FUNC(myarc_fdc_device::fdc_mon_w));
+	m_wd1770->set_disable_motor_control(true);
+
 	m_wd1772->intrq_wr_callback().set(FUNC(myarc_fdc_device::fdc_irq_w));
 	m_wd1772->drq_wr_callback().set(FUNC(myarc_fdc_device::fdc_drq_w));
+	m_wd1772->mon_wr_callback().set(FUNC(myarc_fdc_device::fdc_mon_w));
+	m_wd1772->set_disable_motor_control(true);
 
 	LS259(config, m_drivelatch); // U10
 	m_drivelatch->q_out_cb<0>().set(FUNC(myarc_fdc_device::den_w));

src/devices/bus/ti99/peb/myarcfdc.h

@@ -52,6 +52,8 @@ private:
 	// Callback methods
 	DECLARE_WRITE_LINE_MEMBER( fdc_irq_w );
 	DECLARE_WRITE_LINE_MEMBER( fdc_drq_w );
+	DECLARE_WRITE_LINE_MEMBER( fdc_mon_w );
+
 	DECLARE_WRITE_LINE_MEMBER( den_w );
 	DECLARE_WRITE_LINE_MEMBER( wdreset_w );
 	DECLARE_WRITE_LINE_MEMBER( sidsel_w );

src/devices/machine/wd_fdc.cpp

@@ -87,7 +87,8 @@ wd_fdc_device_base::wd_fdc_device_base(const machine_config &mconfig, device_typ
 	enp_cb(*this),
 	sso_cb(*this),
 	ready_cb(*this), // actually output by the drive, not by the FDC
-	enmf_cb(*this)
+	enmf_cb(*this),
+	mon_cb(*this)
 {
 	force_ready = false;
 	disable_motor_control = false;
@@ -113,6 +114,7 @@ void wd_fdc_device_base::device_start()
 	sso_cb.resolve();
 	ready_cb.resolve();
 	enmf_cb.resolve();
+	mon_cb.resolve_safe();
 
 	if (!has_enmf && !enmf_cb.isnull())
 		logerror("Warning, this chip doesn't have an ENMF line.\n");
@@ -217,6 +219,9 @@ void wd_fdc_device_base::set_floppy(floppy_image_device *_floppy)
 
 	int next_ready = floppy ? floppy->ready_r() : 1;
 
+	if (motor_control)
+		mon_cb(status & S_MON ? 0 : 1);
+
 	if(floppy) {
 		if(motor_control && !disable_motor_control)
 			floppy->mon_w(status & S_MON ? 0 : 1);
@@ -1296,6 +1301,8 @@ void wd_fdc_device_base::spinup()
 	}
 
 	status |= S_MON|S_SPIN;
+
+	mon_cb(0);
 	if(floppy && !disable_motor_control)
 		floppy->mon_w(0);
 }
@@ -1335,6 +1342,7 @@ void wd_fdc_device_base::index_callback(floppy_image_device *floppy, int state)
 			motor_timeout ++;
 			if(motor_control && motor_timeout >= 5) {
 				status &= ~S_MON;
+				mon_cb(1);
 				if(floppy && !disable_motor_control)
 					floppy->mon_w(1);
 			}

src/devices/machine/wd_fdc.h

@@ -57,6 +57,8 @@ public:
 	auto ready_wr_callback() { return ready_cb.bind(); }
 	auto enmf_rd_callback() { return enmf_cb.bind(); }
 
+	auto mon_wr_callback() { return mon_cb.bind(); }
+
 	void soft_reset();
 
 	DECLARE_WRITE_LINE_MEMBER(dden_w);
@@ -295,6 +297,7 @@ private:
 
 	devcb_write_line intrq_cb, drq_cb, hld_cb, enp_cb, sso_cb, ready_cb;
 	devcb_read_line enmf_cb;
+	devcb_write_line mon_cb;
 
 	uint8_t format_last_byte;
 	int format_last_byte_count;