pal.cpp

// license:BSD-3-Clause
// copyright-holders:Nigel Barnes
/***************************************************************************

    BBC Micro PALPROM carrier boards

  Computer Concepts PALPROM carrier boards (PAL16R4):
    These were the first to provide a 32K ROM banked into a 16K slot using
    a PAL to perform the switching upon reads from pre-programmed zones. In
    addition to being able to provide larger ROM based applications such
    as Inter-Word and Inter-Base, it also served as copy protection since
    the carrier board and PAL would have to be reproduced to support the
    ROM.
    Other publishers such as Beebug and PMS also used the carrier boards
    and PAL provided by Computer Concepts.

  Watford Electronics PALPROM carrier boards (PAL16L8):
    The PALPROM device provides a means of running 32K software within the
    space allocated to a 16K sideways ROM whilst providing a good degree of
    software protection.
    Within a PALPROM, a 32K EPROM is divided into 4 banks of 8K. These are
    arranged in a 3 plus 1 arrangement. Bank 0, which occupies &8000 to
    &9FFF is permanently enabled, whilst banks 1 to 3, which occupy the
    region &A000 to &BFFF, are swapped in one at a time. This swapping is
    made by performing an access to a special switching zone, of which there
    are 8 in total. Accessing a switching zone, which is 32 bytes in length
    and aligned to start on a 32 byte boundary, selects a pre-specified bank
    (1 to 3)

  P.R.E.S. PALPROM carrier boards:
    This was based on the Computer Concepts carrier board.

  Instant Mini Office 2:
    Not a PALPROM carrier board but a larger ROM carrier containing 4x32K
    and TTL circuits to enable and page each ROM into 16K banks.

  Acornsoft Trilogy Emulator (PAL20R4)
    An unreleased product that combines the View family of ROMs into a
    single banked 64K ROM, using a PAL to perform 16K bank switches upon
    reads from the last 4 bytes of ROM space &BFFC to &BFFF. Only known
    example loaned by Stuart Swales.

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

#include "emu.h"
#include "pal.h"


//**************************************************************************
//  DEVICE DEFINITIONS
//**************************************************************************

DEFINE_DEVICE_TYPE(BBC_CCIWORD, bbc_cciword_device, "bbc_cciword", "Computer Concepts 32K ROM Carrier (Inter-Word)")
DEFINE_DEVICE_TYPE(BBC_CCIBASE, bbc_ccibase_device, "bbc_ccibase", "Computer Concepts 64K ROM Carrier (Inter-Base)")
DEFINE_DEVICE_TYPE(BBC_CCISPELL, bbc_ccispell_device, "bbc_ccispell", "Computer Concepts 128K ROM Carrier (SpellMaster)")
DEFINE_DEVICE_TYPE(BBC_PALQST, bbc_palqst_device, "bbc_palqst", "Watford Electronics ROM Carrier (Quest Paint)")
DEFINE_DEVICE_TYPE(BBC_PALWAP, bbc_palwap_device, "bbc_palwap", "Watford Electronics ROM Carrier (Wapping Editor)")
DEFINE_DEVICE_TYPE(BBC_PALTED, bbc_palted_device, "bbc_palted", "Watford Electronics ROM Carrier (TED)")
DEFINE_DEVICE_TYPE(BBC_PALABEP, bbc_palabep_device, "bbc_palabep", "P.R.E.S. 32K ROM Carrier (ABE+)")
DEFINE_DEVICE_TYPE(BBC_PALABE, bbc_palabe_device, "bbc_palabe", "P.R.E.S. 32K ROM Carrier (ABE)")
DEFINE_DEVICE_TYPE(BBC_PALMO2, bbc_palmo2_device, "bbc_palmo2", "Instant Mini Office 2 ROM Carrier")
DEFINE_DEVICE_TYPE(BBC_TRILOGY, bbc_trilogy_device, "bbc_trilogy", "Acornsoft Trilogy Emulator")


//**************************************************************************
//  LIVE DEVICE
//**************************************************************************

//-------------------------------------------------
//  bbc_palprom_device - constructor
//-------------------------------------------------

bbc_pal_device::bbc_pal_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock)
	: device_t(mconfig, type, tag, owner, clock)
	, device_bbc_rom_interface(mconfig, *this)
	, m_bank(0)
{
}

bbc_cciword_device::bbc_cciword_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_CCIWORD, tag, owner, clock)
{
}

bbc_ccibase_device::bbc_ccibase_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_CCIBASE, tag, owner, clock)
{
}

bbc_ccispell_device::bbc_ccispell_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_CCISPELL, tag, owner, clock)
{
}

bbc_palqst_device::bbc_palqst_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALQST, tag, owner, clock)
{
}

bbc_palwap_device::bbc_palwap_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALWAP, tag, owner, clock)
{
}

bbc_palted_device::bbc_palted_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALTED, tag, owner, clock)
{
}

bbc_palabep_device::bbc_palabep_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALABEP, tag, owner, clock)
{
}

bbc_palabe_device::bbc_palabe_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALABE, tag, owner, clock)
{
}

bbc_palmo2_device::bbc_palmo2_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_PALMO2, tag, owner, clock)
{
}

bbc_trilogy_device::bbc_trilogy_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
	: bbc_pal_device(mconfig, BBC_TRILOGY, tag, owner, clock)
{
}


//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

void bbc_pal_device::device_start()
{
	save_item(NAME(m_bank));
}

//-------------------------------------------------
//  read
//-------------------------------------------------

uint8_t bbc_cciword_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Inter-Word */
		switch (offset & 0x3fe0)
		{
		case 0x0060:
		case 0x3fc0: m_bank = 0; break;
		case 0x0040:
		case 0x3fa0:
		case 0x3fe0: m_bank = 1; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}

uint8_t bbc_ccibase_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Inter-Base */
		switch (offset & 0x3fe0)
		{
		case 0x3f80: m_bank = 0; break;
		case 0x3fa0: m_bank = 1; break;
		case 0x3fc0: m_bank = 2; break;
		case 0x3fe0: m_bank = 3; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}

uint8_t bbc_ccispell_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for SpellMaster */
		if (offset == 0x3fe0)
		{
			m_bank = 0;
		}
		else if (m_bank == 0)
		{
			switch (offset & 0x3fe0)
			{
			case 0x3fc0: m_bank = 1; break;
			case 0x3fa0: m_bank = 2; break;
			case 0x3f80: m_bank = 3; break;
			case 0x3f60: m_bank = 4; break;
			case 0x3f40: m_bank = 5; break;
			case 0x3f20: m_bank = 6; break;
			case 0x3f00: m_bank = 7; break;
			}
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}

uint8_t bbc_palqst_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Quest Paint and ConQuest */
		switch (offset & 0x3fe0)
		{
		case 0x0820: m_bank = 2; break;
		case 0x11e0: m_bank = 1; break;
		case 0x12c0: m_bank = 3; break;
		case 0x1340: m_bank = 0; break;
		}
	}

	if (offset & 0x2000)
	{
		return get_rom_base()[(offset & 0x1fff) | (m_bank << 13)];
	}
	else
	{
		return get_rom_base()[offset & 0x1fff];
	}
}

uint8_t bbc_palwap_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Wapping Editor */
		switch (offset & 0x3fe0)
		{
		case 0x1f00: m_bank = 0; break;
		case 0x1f20: m_bank = 1; break;
		case 0x1f40: m_bank = 2; break;
		case 0x1f60: m_bank = 3; break;
		case 0x1f80: m_bank = 4; break;
		case 0x1fa0: m_bank = 5; break;
		case 0x1fc0: m_bank = 6; break;
		case 0x1fe0: m_bank = 7; break;
		}
	}

	if (offset & 0x2000)
	{
		return get_rom_base()[(offset & 0x1fff) | (m_bank << 13)];
	}
	else
	{
		return get_rom_base()[offset & 0x1fff];
	}
}

uint8_t bbc_palted_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for TED */
		switch (offset & 0x3fe0)
		{
		case 0x1f80: m_bank = 0; break;
		case 0x1fa0: m_bank = 1; break;
		case 0x1fc0: m_bank = 2; break;
		case 0x1fe0: m_bank = 3; break;
		}
	}

	if (offset & 0x2000)
	{
		return get_rom_base()[(offset & 0x1fff) | (m_bank << 13)];
	}
	else
	{
		return get_rom_base()[offset & 0x1fff];
	}
}

uint8_t bbc_palabep_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Advanced BASIC Editor Plus */
		switch (offset & 0x3ffc)
		{
		case 0x3ff8: m_bank = 0; break;
		case 0x3ffc: m_bank = 1; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}

uint8_t bbc_palabe_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Advanced BASIC Editor */
		switch (offset & 0x3ffc)
		{
		case 0x3ff8: m_bank = 1; break;
		case 0x3ffc: m_bank = 0; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}

uint8_t bbc_palmo2_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Instant Mini Office 2 */
		switch (offset & 0x3ff0)
		{
		case 0x2000: m_bank = offset & 0x0f; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 13)];
}

uint8_t bbc_trilogy_device::read(offs_t offset)
{
	if (!machine().side_effects_disabled())
	{
		/* switching zones for Acornsoft Trilogy Emulator */
		switch (offset & 0x3ff8)
		{
		case 0x3ff8: m_bank = offset & 0x03; break;
		}
	}

	return get_rom_base()[(offset & 0x3fff) | (m_bank << 14)];
}