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Diffstat (limited to 'src/mess/machine/6883sam.h')
-rw-r--r-- | src/mess/machine/6883sam.h | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/src/mess/machine/6883sam.h b/src/mess/machine/6883sam.h new file mode 100644 index 00000000000..09c06dc8fce --- /dev/null +++ b/src/mess/machine/6883sam.h @@ -0,0 +1,229 @@ +/*************************************************************************** + + 6883sam.h + + Motorola 6883 Synchronous Address Multiplexer + +***************************************************************************/ + +#pragma once + +#ifndef __6883SAM__ +#define __6883SAM__ + +#include "emu.h" + +#define MCFG_SAM6883_ADD(_tag, _clock, _config) \ + MCFG_DEVICE_ADD(_tag, SAM6883, _clock) \ + MCFG_DEVICE_CONFIG(_config) + + +/* interface */ +typedef struct _sam6883_interface sam6883_interface; +struct _sam6883_interface +{ + /* the CPU/space from which the SAM reads data */ + const char * m_cpu_tag; + address_spacenum m_cpu_space; + + /* function for reading from memory for video */ + devcb_read8 m_input_func; +}; + + +//************************************************************************** +// SAM6883 CORE +//************************************************************************** + +// base class so that GIME emulation can use some functionality +class sam6883_friend_device +{ +public: + sam6883_friend_device() { m_cpu = NULL; m_sam_state = 0x0000; } + +protected: + // SAM state constants + static const UINT16 SAM_STATE_TY = 0x8000; + static const UINT16 SAM_STATE_M1 = 0x4000; + static const UINT16 SAM_STATE_M0 = 0x2000; + static const UINT16 SAM_STATE_R1 = 0x1000; + static const UINT16 SAM_STATE_R0 = 0x0800; + static const UINT16 SAM_STATE_P1 = 0x0400; + static const UINT16 SAM_STATE_F6 = 0x0200; + static const UINT16 SAM_STATE_F5 = 0x0100; + static const UINT16 SAM_STATE_F4 = 0x0080; + static const UINT16 SAM_STATE_F3 = 0x0040; + static const UINT16 SAM_STATE_F2 = 0x0020; + static const UINT16 SAM_STATE_F1 = 0x0010; + static const UINT16 SAM_STATE_F0 = 0x0008; + static const UINT16 SAM_STATE_V2 = 0x0004; + static const UINT16 SAM_STATE_V1 = 0x0002; + static const UINT16 SAM_STATE_V0 = 0x0001; + + // incidentals + cpu_device * m_cpu; + + // device state + UINT16 m_sam_state; + + ATTR_FORCE_INLINE UINT16 display_offset(void) + { + 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 alter_sam_state(offs_t offset) + { + /* determine the mask */ + UINT16 mask = 1 << (offset >> 1); + + /* determine the new state */ + UINT16 new_state; + if (offset & 0x0001) + new_state = m_sam_state | mask; + else + new_state = m_sam_state & ~mask; + + /* specify the new state */ + UINT16 xorval = m_sam_state ^ new_state; + m_sam_state = new_state; + return xorval; + } + + void update_cpu_clock(void); +}; + +class sam6883_device : public device_t, public sam6883_friend_device +{ +public: + sam6883_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock); + + // called to configure banks + void configure_bank(int bank, UINT8 *memory, UINT32 memory_size, bool is_read_only); + void configure_bank(int bank, read8_delegate rhandler, write8_delegate whandler); + + // typically called by VDG + ATTR_FORCE_INLINE DECLARE_READ8_MEMBER( display_read ) + { + 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_res_input_func(m_counter); + } + + DECLARE_WRITE_LINE_MEMBER( hs_w ); + + // typically called by machine + address_space *mpu_address_space(void) const { return m_cpu_space; } + void set_bank_offset(int bank, offs_t offset); + +protected: + // device-level overrides + virtual void device_start(); + virtual void device_reset(); + virtual void device_post_load(); + +private: + struct sam_bank + { + UINT8 * m_memory; + UINT32 m_memory_size; + offs_t m_memory_offset; + bool m_memory_read_only; + read8_delegate m_rhandler; + write8_delegate m_whandler; + }; + + // incidentals + address_space * m_cpu_space; + devcb_resolved_read8 m_res_input_func; + sam_bank m_banks[8]; + + // SAM state + UINT16 m_counter; + UINT8 m_counter_xdiv; + UINT8 m_counter_ydiv; + + // typically called by CPU + DECLARE_READ8_MEMBER( read ); + DECLARE_WRITE8_MEMBER( write ); + + // called when there is a carry out of bit 3 on the counter + ATTR_FORCE_INLINE void counter_carry_bit3(void) + { + UINT8 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"); + 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(void) + { + UINT8 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"); + return; + } + + if (++m_counter_ydiv >= y_division) + { + m_counter_ydiv = 0; + m_counter += 0x0020; + } + } + + // other members + void configure_bank(int bank, UINT8 *memory, UINT32 memory_size, bool is_read_only, read8_delegate rhandler, write8_delegate whandler); + void horizontal_sync(void); + void update_state(void); + void update_memory(void); + void update_bank(int bank, offs_t addrstart, offs_t addrend, offs_t offset); + void install_memory(offs_t addrstart, offs_t addrend, void *memory, bool is_read_only); +}; + +extern const device_type SAM6883; + +#endif /* __6883SAM__ */ |