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// license:BSD-3-Clause
// copyright-holders:AJR
/**********************************************************************
Seals Electronics 8K SC RAM board
PolyMorphic Systems used this S-100 memory board in their first
series of computers before introducing a 16K dynamic RAM of their
own design.
The 8K SC originally used AMD 91L02APC 1024x1 static RAMs with a
500 ns access time. Replacing these with faster RAMs was certainly
possible (the 8K SC-Z kit was supplied with the 250 ns 2102LHPC),
and essential for use with high-speed CPUs since the tightly-
packed board had absolutely no room for a wait state circuit.
The 8K SC could be configured for battery backup by providing +2
to +4 V at 600 mA on pin 14. (Pin 14 also could provide standby
power to static RAM boards by Ithaca Audio, but this use was
incompatible with some other S-100 systems and not sanctioned by
the IEEE-696 standard). Power for this prominently advertised yet
entirely optional feature was supplied by a Battery Back-Up Card
(BBUC) which Seals sold separately. However, 64 static RAM chips
made the 8K SC rather power-hungry even when operating under
normal power (which it drew through four 7805 voltage regulators).
**********************************************************************/
#include "emu.h"
#include "seals8k.h"
//**************************************************************************
// TYPE DEFINITIONS
//**************************************************************************
// ======================> s100_8k_sc_device
class s100_8k_sc_device : public device_t, public device_s100_card_interface
{
public:
// construction/destruction
s100_8k_sc_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
protected:
// delegated construction
s100_8k_sc_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, u32 clock);
// device-specific overrides
virtual ioport_constructor device_input_ports() const override;
virtual void device_start() override;
// S-100 memory access handlers
virtual u8 s100_smemr_r(offs_t offset) override;
virtual void s100_mwrt_w(offs_t offset, u8 data) override;
// internal state
std::unique_ptr<u8[]> m_ram;
private:
// helpers
bool board_selected(offs_t offset) const;
// object finder
required_ioport m_dsw;
};
// ======================> s100_8k_sc_bb_device
class s100_8k_sc_bb_device : public s100_8k_sc_device, public device_nvram_interface
{
public:
// construction/destruction
s100_8k_sc_bb_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock);
protected:
// device_nvram_interface overrides
virtual void nvram_read(emu_file &file) override;
virtual void nvram_write(emu_file &file) override;
virtual void nvram_default() override;
};
DEFINE_DEVICE_TYPE_PRIVATE(S100_8K_SC, device_s100_card_interface, s100_8k_sc_device, "s100_8k_sc", "Seals 8K SC Memory Board")
DEFINE_DEVICE_TYPE_PRIVATE(S100_8K_SC_BB, device_s100_card_interface, s100_8k_sc_bb_device, "s100_8k_sc_bb", "Seals 8K SC Memory Board with Battery Backup")
template class device_finder<device_s100_card_interface, false>;
template class device_finder<device_s100_card_interface, true>;
//**************************************************************************
// CONFIGURATION SETTINGS
//**************************************************************************
static INPUT_PORTS_START( s100_8k_sc )
PORT_START("DSW")
PORT_DIPNAME(0xff, 0xfb, "Address Range") PORT_DIPLOCATION("IC67:1,2,3,4,5,6,7,8")
PORT_DIPSETTING(0xfe, "0 to 8K")
PORT_DIPSETTING(0xfd, "8K to 16K")
PORT_DIPSETTING(0xfb, "16K to 24K")
PORT_DIPSETTING(0xf7, "24K to 32K")
PORT_DIPSETTING(0xef, "32K to 40K")
PORT_DIPSETTING(0xdf, "40K to 48K")
PORT_DIPSETTING(0xbf, "48K to 56K")
PORT_DIPSETTING(0x7f, "56K to 64K")
INPUT_PORTS_END
//**************************************************************************
// DEVICE DEFINITION
//**************************************************************************
//-------------------------------------------------
// s100_8k_sc_device - constructor
//-------------------------------------------------
s100_8k_sc_device::s100_8k_sc_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, u32 clock) :
device_t(mconfig, type, tag, owner, clock),
device_s100_card_interface(mconfig, *this),
m_dsw(*this, "DSW")
{
}
s100_8k_sc_device::s100_8k_sc_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock) :
s100_8k_sc_device(mconfig, S100_8K_SC, tag, owner, clock)
{
}
//-------------------------------------------------
// s100_8k_sc_bb_device - constructor
//-------------------------------------------------
s100_8k_sc_bb_device::s100_8k_sc_bb_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock) :
s100_8k_sc_device(mconfig, S100_8K_SC_BB, tag, owner, clock),
device_nvram_interface(mconfig, *this)
{
}
//-------------------------------------------------
// device_input_ports - input port construction
//-------------------------------------------------
ioport_constructor s100_8k_sc_device::device_input_ports() const
{
return INPUT_PORTS_NAME(s100_8k_sc);
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void s100_8k_sc_device::device_start()
{
m_ram = make_unique_clear<u8[]>(0x2000);
save_pointer(NAME(m_ram), 0x2000);
}
//-------------------------------------------------
// nvram_read - read NVRAM from the file
//-------------------------------------------------
void s100_8k_sc_bb_device::nvram_read(emu_file &file)
{
file.read(m_ram.get(), 0x2000);
}
//------------------------------------------------
// nvram_write - write NVRAM to the file
//-------------------------------------------------
void s100_8k_sc_bb_device::nvram_write(emu_file &file)
{
file.write(m_ram.get(), 0x2000);
}
//------------------------------------------------
// nvram_default - default NVRAM setting
//-------------------------------------------------
void s100_8k_sc_bb_device::nvram_default()
{
}
//-------------------------------------------------
// board_selected - return true if the address
// is within the board's configured range
//-------------------------------------------------
bool s100_8k_sc_device::board_selected(offs_t offset) const
{
// A13-A15 decoded by 74138 at IC66
return (m_dsw->read() | 1 << ((offset >> 13) & 7)) == 0xff;
}
//-------------------------------------------------
// s100_smemr_r - memory read
//-------------------------------------------------
u8 s100_8k_sc_device::s100_smemr_r(offs_t offset)
{
if (board_selected(offset))
return m_ram[offset & 0x1fff];
else
return 0xff;
}
//-------------------------------------------------
// s100_mwrt_w - memory write
//-------------------------------------------------
void s100_8k_sc_device::s100_mwrt_w(offs_t offset, u8 data)
{
if (board_selected(offset))
m_ram[offset & 0x1fff] = data;
}
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