olivetti/m20: handle segment trap in driver

Author: tpaxia

src/devices/bus/zbi/s8k_cpu.cpp

@@ -656,7 +656,6 @@ void zbi_s8k_cpu10_card_device::centronics_ack_w(uint8_t data)
 void zbi_s8k_cpu10_card_device::device_add_mconfig(machine_config &config)
 {
 	Z8001(config, m_maincpu, CLK_CPU);
-	m_maincpu->set_m20_hack(false);
 	m_maincpu->set_addrmap(AS_PROGRAM, &zbi_s8k_cpu10_card_device::addrmap_program);
 	m_maincpu->set_addrmap(AS_DATA, &zbi_s8k_cpu10_card_device::addrmap_data);
 	m_maincpu->set_addrmap(z8001_device::AS_STACK, &zbi_s8k_cpu10_card_device::addrmap_stack);
@@ -1228,7 +1227,6 @@ void zbi_s8k_hpcpu_card_device::device_resolve_objects()
 void zbi_s8k_hpcpu_card_device::device_add_mconfig(machine_config &config)
 {
 	Z8001(config, m_maincpu, CLK_HPCPU);
-	m_maincpu->set_m20_hack(false);
 	m_maincpu->set_addrmap(AS_PROGRAM, &zbi_s8k_hpcpu_card_device::addrmap_program);
 	m_maincpu->set_addrmap(AS_DATA, &zbi_s8k_hpcpu_card_device::addrmap_data);
 	m_maincpu->set_addrmap(z8001_device::AS_STACK, &zbi_s8k_hpcpu_card_device::addrmap_stack);

src/devices/cpu/z8000/z8000.cpp

@@ -42,7 +42,7 @@ z8002_device::z8002_device(const machine_config &mconfig, device_type type, cons
 	, m_ns_out(*this)
 	, m_busack_out(*this)
 	, m_ppc(0), m_pc(0), m_psapseg(0), m_psapoff(0), m_fcw(0), m_refresh(0), m_nspseg(0), m_nspoff(0), m_irq_req(0), m_irq_vec(0), m_op_valid(0), m_nmi_state(0), m_busreq_state(0), m_busack_state(0), m_mi(0), m_halt(false), m_icount(0)
-	, m_vector_mult(vecmult), m_m20_hack(true)
+	, m_vector_mult(vecmult)
 {
 }
 
@@ -202,11 +202,6 @@ uint16_t z8002_device::RDMEM_W(memory_access<23, 1, 0, ENDIANNESS_BIG>::specific
 {
 	addr = adjust_addr_for_nonseg_mode(addr);
 	addr &= ~1;
-	/* hack for m20 driver: BIOS accesses 0x7f0000 and expects a segmentation violation */
-	if (m_m20_hack && (addr >= 0x7f0000)) {
-		m_irq_req = Z8000_SEGTRAP;
-		return 0xffff;
-	}
 	return space.read_word(addr);
 }
 

src/devices/cpu/z8000/z8000.h

@@ -112,7 +112,6 @@ class z8002_device : public cpu_device, public z8000_disassembler::config
 	auto ns() { return m_ns_out.bind(); }
 
 	bool is_ifetch1() const noexcept { return (m_op_valid == 0); }
-	void set_m20_hack(bool is_hack) { m_m20_hack = is_hack; }
 
 protected:
 	z8002_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock, int addrbits, int vecmult);
@@ -187,7 +186,6 @@ class z8002_device : public cpu_device, public z8000_disassembler::config
 	memory_access<16, 1, 0, ENDIANNESS_BIG>::specific m_sio;
 	int m_icount;
 	const int m_vector_mult;
-	bool m_m20_hack;
 
 	void clear_internal_state();
 	void register_debug_state();

src/mame/olivetti/m20.cpp

@@ -122,6 +122,8 @@ class m20_state : public driver_device
 	void install_memory();
 
 	static void floppy_formats(format_registration &fr);
+	uint16_t segment_r();
+	uint16_t segtack_r();
 	uint16_t viack_r();
 	uint16_t nviack_r();
 };
@@ -330,12 +332,14 @@ void m20_state::m20_program_mem(address_map &map)
 {
 	map.unmap_value_high();
 	map(0x40000, 0x41fff).rom().region("maincpu", 0x00000);
+	map(0x7f0000, 0x7fffff).r(FUNC(m20_state::segment_r));
 }
 
 void m20_state::m20_data_mem(address_map &map)
 {
 	map.unmap_value_high();
 	map(0x40000, 0x41fff).rom().region("maincpu", 0x00000);
+	map(0x7f0000, 0x7fffff).r(FUNC(m20_state::segment_r));
 }
 
 
@@ -692,6 +696,20 @@ uint16_t m20_state::viack_r()
 	return m_i8259->acknowledge()<<1;
 }
 
+uint16_t m20_state::segment_r()
+{
+	if (!machine().side_effects_disabled())
+		m_maincpu->set_input_line(z8001_device::SEGT_LINE, ASSERT_LINE);
+
+	return 0xffff;
+}
+
+uint16_t m20_state::segtack_r()
+{
+	m_maincpu->set_input_line(z8001_device::SEGT_LINE, CLEAR_LINE);
+	return 0xffff;
+}
+
 uint16_t m20_state::nviack_r()
 {
 	m_maincpu->set_input_line(z8001_device::NVI_LINE, CLEAR_LINE);
@@ -770,6 +788,7 @@ void m20_state::m20(machine_config &config)
 	m_maincpu->set_addrmap(AS_PROGRAM, &m20_state::m20_program_mem);
 	m_maincpu->set_addrmap(AS_DATA, &m20_state::m20_data_mem);
 	m_maincpu->set_addrmap(AS_IO, &m20_state::m20_io);
+	m_maincpu->segtack().set(FUNC(m20_state::segtack_r));
 	m_maincpu->viack().set(FUNC(m20_state::viack_r));
 	m_maincpu->nviack().set(FUNC(m20_state::nviack_r));