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+// 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);
+ }
+
+ void hs_w(int state);
+
+protected:
+ // device-level overrides
+ virtual void device_start() override ATTR_COLD;
+ virtual void device_reset() override ATTR_COLD;
+ virtual void device_post_load() override;
+
+ // device_memory_interface overrides
+ virtual space_config_vector memory_space_config() const override;
+
+private:
+ // memory space configuration
+ 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 = 0;
+
+ // SAM state
+ uint16_t m_counter = 0;
+ uint8_t m_counter_xdiv = 0;
+ uint8_t m_counter_ydiv = 0;
+
+ // 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