pps41: add serial i/o

src/devices/cpu/pps41/mm75.h

@@ -42,6 +42,9 @@ public:
 protected:
 	virtual void device_start() override;
 
+	virtual u32 execute_input_lines() const noexcept override { return 2; }
+	virtual void execute_set_input(int line, int state) override { if (line < 2) mm76_device::execute_set_input(line, state); }
+
 	// opcode handlers
 	virtual void op_ios() override;
 	virtual void op_i2c() override;

src/devices/cpu/pps41/mm76op.cpp

@@ -175,12 +175,14 @@ void mm76_device::op_xas()
 	u8 a = m_a;
 	m_a = m_s;
 	m_s = a;
+	m_write_sdo(BIT(m_s, 3));
 }
 
 void mm76_device::op_lsa()
 {
 	// LSA: load S from A
 	m_s = m_a;
+	m_write_sdo(BIT(m_s, 3));
 }
 
 
@@ -413,7 +415,7 @@ void mm76_device::op_oa()
 void mm76_device::op_ios()
 {
 	// IOS: start serial I/O
-	op_todo();
+	m_sclock_count = 8;
 }
 
 void mm76_device::op_i1()

src/devices/cpu/pps41/pps41base.cpp

@@ -40,7 +40,6 @@ TODO:
   flops with SOS/ROS opcodes
 - allowed opcodes after TAB should be limited
 - add MCU mask options, there's one for inverting interrupts
-- add serial i/o
 - add MM78LA
 
 */
@@ -62,7 +61,9 @@ pps41_base_device::pps41_base_device(const machine_config &mconfig, device_type
 	m_read_d(*this),
 	m_write_d(*this),
 	m_read_r(*this),
-	m_write_r(*this)
+	m_write_r(*this),
+	m_write_sdo(*this),
+	m_write_ssc(*this)
 { }
 
 
@@ -83,6 +84,8 @@ void pps41_base_device::device_start()
 	m_write_d.resolve_safe();
 	m_read_r.resolve_safe(0xff);
 	m_write_r.resolve_safe();
+	m_write_sdo.resolve_safe();
+	m_write_ssc.resolve_safe();
 
 	// init RAM with 0xf
 	for (int i = 0; i <= m_datamask; i++)
@@ -108,16 +111,21 @@ void pps41_base_device::device_start()
 	m_prev_c = 0;
 	m_c_in = 0;
 	m_c_delay = false;
-	m_s = 0;
 	m_x = 0;
 	m_skip = false;
 	m_skip_count = 0;
 
+	m_s = 0;
+	m_sdi = 0;
+	m_sclock_in = 0;
+	m_sclock_count = 0;
+	m_ss_pending = false;
+
 	m_d_pins = 10;
 	m_d_mask = (1 << m_d_pins) - 1;
 	m_d_output = 0;
 	m_r_output = 0;
-	m_int_line[0] = m_int_line[1] = 1;
+	m_int_line[0] = m_int_line[1] = 0;
 	m_int_ff[0] = m_int_ff[1] = 0;
 
 	// register for savestates
@@ -140,11 +148,16 @@ void pps41_base_device::device_start()
 	save_item(NAME(m_prev_c));
 	save_item(NAME(m_c_in));
 	save_item(NAME(m_c_delay));
-	save_item(NAME(m_s));
 	save_item(NAME(m_x));
 	save_item(NAME(m_skip));
 	save_item(NAME(m_skip_count));
 
+	save_item(NAME(m_s));
+	save_item(NAME(m_sdi));
+	save_item(NAME(m_sclock_in));
+	save_item(NAME(m_sclock_count));
+	save_item(NAME(m_ss_pending));
+
 	save_item(NAME(m_d_output));
 	save_item(NAME(m_r_output));
 	save_item(NAME(m_int_line));
@@ -187,6 +200,11 @@ void pps41_base_device::device_reset()
 	// clear outputs
 	m_write_r(m_r_output = 0xff);
 	m_write_d(m_d_output = 0);
+
+	m_s = 0;
+	m_sclock_count = 0;
+	m_write_sdo(0);
+	m_write_ssc(0);
 }
 
 
@@ -214,6 +232,17 @@ void pps41_base_device::execute_set_input(int line, int state)
 			m_int_line[1] = state;
 			break;
 
+		case PPS41_INPUT_LINE_SDI:
+			m_sdi = state;
+			break;
+
+		case PPS41_INPUT_LINE_SSC:
+			// serial shift pending on falling edge
+			if (!state && m_sclock_in)
+				m_ss_pending = true;
+			m_sclock_in = state;
+			break;
+
 		default:
 			break;
 	}
@@ -227,6 +256,21 @@ void pps41_base_device::execute_set_input(int line, int state)
 void pps41_base_device::cycle()
 {
 	m_icount--;
+
+	// clock serial i/o
+	m_ss_pending = m_ss_pending || bool(m_sclock_count & 1);
+
+	if (m_sclock_count)
+	{
+		m_sclock_count--;
+		m_write_ssc(m_sclock_count & 1);
+	}
+	if (m_ss_pending)
+	{
+		m_ss_pending = false;
+		m_s = (m_s << 1 | m_sdi) & 0xf;
+		m_write_sdo(BIT(m_s, 3));
+	}
 }
 
 void pps41_base_device::increment_pc()

src/devices/cpu/pps41/pps41base.h

@@ -16,7 +16,9 @@
 enum
 {
 	PPS41_INPUT_LINE_INT0 = 0,
-	PPS41_INPUT_LINE_INT1
+	PPS41_INPUT_LINE_INT1,
+	PPS41_INPUT_LINE_SDI, // serial data input
+	PPS41_INPUT_LINE_SSC // serial shift clock
 };
 
 
@@ -37,6 +39,10 @@ public:
 	auto read_r() { return m_read_r.bind(); }
 	auto write_r() { return m_write_r.bind(); }
 
+	// serial data/clock
+	auto write_sdo() { return m_write_sdo.bind(); }
+	auto write_ssc() { return m_write_ssc.bind(); }
+
 protected:
 	// construction/destruction
 	pps41_base_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, u32 clock, int prgwidth, address_map_constructor program, int datawidth, address_map_constructor data);
@@ -48,7 +54,7 @@ protected:
 	// device_execute_interface overrides
 	virtual u32 execute_min_cycles() const noexcept override { return 1; }
 	virtual u32 execute_max_cycles() const noexcept override { return 2; }
-	virtual u32 execute_input_lines() const noexcept override { return 2; }
+	virtual u32 execute_input_lines() const noexcept override { return 4; }
 	virtual void execute_set_input(int line, int state) override;
 	virtual void execute_run() override;
 	virtual void execute_one() = 0;
@@ -78,6 +84,8 @@ protected:
 	devcb_write16 m_write_d;
 	devcb_read8 m_read_r;
 	devcb_write8 m_write_r;
+	devcb_write_line m_write_sdo;
+	devcb_write_line m_write_ssc;
 
 	// internal state, regs
 	u16 m_pc;
@@ -100,11 +108,16 @@ protected:
 	int m_prev_c;
 	int m_c_in;
 	bool m_c_delay;
-	u8 m_s;
 	u8 m_x;
 	bool m_skip;
 	int m_skip_count;
 
+	u8 m_s;
+	int m_sdi;
+	int m_sclock_in;
+	int m_sclock_count;
+	bool m_ss_pending;
+
 	int m_d_pins;
 	u16 m_d_mask;
 	u16 m_d_output;