t11: power fail trap is NMI, added bus error trap

src/devices/cpu/t11/t11.cpp

@@ -52,6 +52,7 @@ t11_device::t11_device(const machine_config &mconfig, device_type type, const ch
 	, m_cp_state(0)
 	, m_vec_active(false)
 	, m_pf_active(false)
+	, m_berr_active(false)
 	, m_hlt_active(false)
 	, m_out_reset_func(*this)
 	, m_in_iack_func(*this)
@@ -222,9 +223,14 @@ void t11_device::t11_check_irqs()
 		return;
 	}
 
-	// PF has next-highest priority
-	int priority = PSW & 0340;
-	if (m_power_fail && priority != 0340)
+	// non-maskable hardware traps
+	if (m_bus_error)
+	{
+		m_bus_error = false;
+		take_interrupt(T11_TIMEOUT);
+		return;
+	}
+	else if (m_power_fail)
 	{
 		m_power_fail = false;
 		take_interrupt(T11_PWRFAIL);
@@ -233,7 +239,7 @@ void t11_device::t11_check_irqs()
 
 	// compare the priority of the CP interrupt to the PSW
 	const struct irq_table_entry *irq = &irq_table[m_cp_state & 15];
-	if (irq->priority > priority)
+	if (irq->priority > (PSW & 0340))
 	{
 		// call the callback
 		standard_irq_callback(m_cp_state & 15);
@@ -404,6 +410,7 @@ void t11_device::device_reset()
 
 	m_wait_state = 0;
 	m_power_fail = false;
+	m_bus_error = false;
 	m_ext_halt = false;
 }
 
@@ -447,6 +454,12 @@ void t11_device::execute_set_input(int irqline, int state)
 		m_pf_active = (state != CLEAR_LINE);
 		break;
 
+	case BUS_ERROR:
+		if (state != CLEAR_LINE && !m_berr_active)
+			m_bus_error = true;
+		m_berr_active = (state != CLEAR_LINE);
+		break;
+
 	case HLT_LINE:
 		if (state != CLEAR_LINE && !m_hlt_active)
 			m_ext_halt = true;

src/devices/cpu/t11/t11.h

@@ -22,6 +22,7 @@ enum
 class t11_device :  public cpu_device
 {
 public:
+	// T11 input lines
 	enum
 	{
 		CP0_LINE = 0,           // -AI4 (at PI time)
@@ -33,8 +34,12 @@ public:
 		HLT_LINE = 6            // -AI7 (at PI time)
 	};
 
+	// generic hardware traps
+	static constexpr uint8_t POWER_FAIL = PF_LINE;
+	static constexpr uint8_t BUS_ERROR = 8;
+
 	// construction/destruction
-	t11_device(const machine_config &mconfig, const char *_tag, device_t *_owner, uint32_t _clock);
+	t11_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
 	// configuration helpers
 	void set_initial_mode(const uint16_t mode) { c_initial_mode = mode; }
@@ -63,8 +68,8 @@ protected:
 	// device_execute_interface overrides
 	virtual uint32_t execute_min_cycles() const noexcept override { return 12; }
 	virtual uint32_t execute_max_cycles() const noexcept override { return 114; }
-	virtual uint32_t execute_input_lines() const noexcept override { return 7; }
-	virtual bool execute_input_edge_triggered(int inputnum) const noexcept override { return inputnum == PF_LINE || inputnum == HLT_LINE; }
+	virtual uint32_t execute_input_lines() const noexcept override { return 8; }
+	virtual bool execute_input_edge_triggered(int inputnum) const noexcept override { return inputnum == PF_LINE || inputnum == HLT_LINE || inputnum == BUS_ERROR; }
 	virtual void execute_run() override;
 	virtual void execute_set_input(int inputnum, int state) override;
 
@@ -89,8 +94,10 @@ protected:
 	uint8_t             m_cp_state;
 	bool                m_vec_active;
 	bool                m_pf_active;
+	bool                m_berr_active;
 	bool                m_hlt_active;
 	bool                m_power_fail;
+	bool                m_bus_error;
 	bool                m_ext_halt;
 	int                 m_icount;
 	memory_access<16, 1, 0, ENDIANNESS_LITTLE>::cache m_cache;

src/mame/drivers/im01.cpp

@@ -18,12 +18,13 @@ TODO:
   and/or T11 core timing itself is not 100% accurate.
 - verify actual XTAL, the label couldn't be seen
 - correct bus conflict between RAM and I/O
+- is ИМ-01Т extra RAM chip used at all?
 
 *******************************************************************************
 
 Hardware notes:
 - К1801ВМ1 CPU (PDP-11 derived) @ ~4.61MHz
-- 16KB ROM (2*К1809РЕ1), 2KB RAM(К1809РУ1)
+- 16KB ROM (2*К1809РЕ1), 2KB RAM(К1809РУ1) (4KB RAM for ИМ-01Т)
 - K1809BB1 (I/O, counter)
 - 4-digit VFD 7seg panel(cyan, green window overlay), beeper