summaryrefslogblamecommitdiffstatshomepage
path: root/src/mame/machine/6883sam.h
blob: d3e7e725e8af6b316aea4c0b5a8b3e02950dfa36 (plain) (tree)
1
2
3
4
5
6
7
8
9
10

                                 







                                                                            

                              
 
            
 
 




                                                                            
                                                               

       
                                                                                                      


                              















                                                    

                      
                                          

                       
                             
 


                                                          
                                                   



                                                                                                                                                          
                                                                 

                                        
                                                   

                                             
                                   





                                                        
                                                          



                                        
                                

  
                                                                                                              

       
                             

                                                                                                                    
         



                                                                                                        
 


                                                

                                  
                                                             

















                                                                                       
                                                                         



                                          
          
                                 


                                                 
 

                                                                         
 











                                                  



                                                                        
                                                   

                    


                                                   

                                  
                                                         

                                                                   
                                                   
         
                                   

                                                                                               







                                                          
                                
                                                                    












                                                                   
                                                   
         
                                   

                                                                                               







                                                              
                                
                                                                    










                                                   


                               

  
                                            
 
                                
// license:BSD-3-Clause
// copyright-holders:Nathan Woods
/***************************************************************************

    6883sam.h

    Motorola 6883 Synchronous Address Multiplexer

***************************************************************************/

#ifndef MAME_MACHINE_6883SAM_H
#define MAME_MACHINE_6883SAM_H

#pragma once


//**************************************************************************
//  SAM6883 CORE
//**************************************************************************

// base class so that GIME emulation can use some functionality
class sam6883_friend_device_interface : public device_interface
{
public:
	sam6883_friend_device_interface(const machine_config &mconfig, device_t &device, int divider);

protected:
	// SAM state constants
	static const uint16_t SAM_STATE_TY = 0x8000;
	static const uint16_t SAM_STATE_M1 = 0x4000;
	static const uint16_t SAM_STATE_M0 = 0x2000;
	static const uint16_t SAM_STATE_R1 = 0x1000;
	static const uint16_t SAM_STATE_R0 = 0x0800;
	static const uint16_t SAM_STATE_P1 = 0x0400;
	static const uint16_t SAM_STATE_F6 = 0x0200;
	static const uint16_t SAM_STATE_F5 = 0x0100;
	static const uint16_t SAM_STATE_F4 = 0x0080;
	static const uint16_t SAM_STATE_F3 = 0x0040;
	static const uint16_t SAM_STATE_F2 = 0x0020;
	static const uint16_t SAM_STATE_F1 = 0x0010;
	static const uint16_t SAM_STATE_F0 = 0x0008;
	static const uint16_t SAM_STATE_V2 = 0x0004;
	static const uint16_t SAM_STATE_V1 = 0x0002;
	static const uint16_t SAM_STATE_V0 = 0x0001;

	// incidentals
	required_device<cpu_device> m_cpu;

	// device state
	uint16_t m_sam_state;

	// base clock divider (/4 for MC6883, /8 for GIME)
	int m_divider;

	ATTR_FORCE_INLINE uint16_t display_offset()
	{
		return ((m_sam_state & (SAM_STATE_F0|SAM_STATE_F1|SAM_STATE_F2|SAM_STATE_F3|SAM_STATE_F4|SAM_STATE_F5|SAM_STATE_F6)) / SAM_STATE_F0) << 9;
	}

	ATTR_FORCE_INLINE uint16_t alter_sam_state(offs_t offset)
	{
		/* determine the mask */
		uint16_t mask = 1 << (offset >> 1);

		/* determine the new state */
		uint16_t new_state;
		if (offset & 0x0001)
			new_state = m_sam_state | mask;
		else
			new_state = m_sam_state & ~mask;

		/* specify the new state */
		uint16_t xorval = m_sam_state ^ new_state;
		m_sam_state = new_state;
		return xorval;
	}

	void update_cpu_clock();
};

class sam6883_device : public device_t, public device_memory_interface, public sam6883_friend_device_interface
{
public:
	template <typename T>
	sam6883_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock, T &&cpu_tag)
		: sam6883_device(mconfig, tag, owner, clock)
	{
		m_cpu.set_tag(std::forward<T>(cpu_tag));
	}

	sam6883_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);

	// CPU read/write handlers
	uint8_t read(offs_t offset);
	void write(offs_t offset, uint8_t data);

	// typically called by VDG
	ATTR_FORCE_INLINE uint8_t display_read(offs_t offset)
	{
		if (offset == (offs_t) ~0)
		{
			/* the VDG is telling the counter to reset */
			m_counter = display_offset();
			m_counter_xdiv = 0;
			m_counter_ydiv = 0;
		}
		else if ((offset & 1) != (m_counter & 0x0001))
		{
			/* DA0 has been toggled - first bump B0-B3 of the counter */
			bool bit3_carry = (m_counter & 0x000F) == 0x000F;
			m_counter = (m_counter & ~0x000F) | ((m_counter + 1) & 0x000F);

			/* and apply the carry (if applicable */
			if (bit3_carry)
				counter_carry_bit3();
		}
		return m_ram_space.read_byte(m_counter & m_counter_mask);
	}

	DECLARE_WRITE_LINE_MEMBER( hs_w );

protected:
	// device-level overrides
	virtual void device_start() override;
	virtual void device_reset() override;
	virtual void device_post_load() override;

	// device_memory_interface overrides
	virtual space_config_vector memory_space_config() const override;

private:
	// memory space configuratino
	address_space_config        m_ram_config;
	address_space_config        m_rom0_config;
	address_space_config        m_rom1_config;
	address_space_config        m_rom2_config;
	address_space_config        m_io0_config;
	address_space_config        m_io1_config;
	address_space_config        m_io2_config;
	address_space_config        m_boot_config;

	// memory spaces
	memory_access<16, 0, 0, ENDIANNESS_BIG>::cache m_ram_space;
	memory_access<14, 0, 0, ENDIANNESS_BIG>::cache m_rom_space[3];
	memory_access< 5, 0, 0, ENDIANNESS_BIG>::specific m_io_space[3];
	memory_access< 7, 0, 0, ENDIANNESS_BIG>::cache m_boot_space;
	uint16_t                    m_counter_mask;

	// SAM state
	uint16_t                    m_counter;
	uint8_t                     m_counter_xdiv;
	uint8_t                     m_counter_ydiv;

	// typically called by CPU
	void internal_write(offs_t offset, uint8_t data);

	// called when there is a carry out of bit 3 on the counter
	ATTR_FORCE_INLINE void counter_carry_bit3()
	{
		uint8_t x_division;
		switch((m_sam_state & (SAM_STATE_V2|SAM_STATE_V1|SAM_STATE_V0)) / SAM_STATE_V0)
		{
			case 0x00:  x_division = 1; break;
			case 0x01:  x_division = 3; break;
			case 0x02:  x_division = 1; break;
			case 0x03:  x_division = 2; break;
			case 0x04:  x_division = 1; break;
			case 0x05:  x_division = 1; break;
			case 0x06:  x_division = 1; break;
			case 0x07:  x_division = 1; break;
			default:
				fatalerror("Should not get here\n");
				return;
		}

		if (++m_counter_xdiv >= x_division)
		{
			m_counter_xdiv = 0;
			m_counter ^= 0x0010;
			if ((m_counter & 0x0010) == 0x0000)
				counter_carry_bit4();
		}
	}

	// called when there is a carry out of bit 4 on the counter
	ATTR_FORCE_INLINE void counter_carry_bit4()
	{
		uint8_t y_division;
		switch((m_sam_state & (SAM_STATE_V2|SAM_STATE_V1|SAM_STATE_V0)) / SAM_STATE_V0)
		{
			case 0x00:  y_division = 12;    break;
			case 0x01:  y_division = 1;     break;
			case 0x02:  y_division = 3;     break;
			case 0x03:  y_division = 1;     break;
			case 0x04:  y_division = 2;     break;
			case 0x05:  y_division = 1;     break;
			case 0x06:  y_division = 1;     break;
			case 0x07:  y_division = 1;     break;
			default:
				fatalerror("Should not get here\n");
				return;
		}

		if (++m_counter_ydiv >= y_division)
		{
			m_counter_ydiv = 0;
			m_counter += 0x0020;
		}
	}

	// other members
	void horizontal_sync();
	void update_state();
	void update_memory();
};

DECLARE_DEVICE_TYPE(SAM6883, sam6883_device)

#endif // MAME_MACHINE_6883SAM_H