diff options
Diffstat (limited to 'src/devices/bus/ti99_peb/samsmem.cpp')
-rw-r--r-- | src/devices/bus/ti99_peb/samsmem.cpp | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/src/devices/bus/ti99_peb/samsmem.cpp b/src/devices/bus/ti99_peb/samsmem.cpp new file mode 100644 index 00000000000..7a8db384ffd --- /dev/null +++ b/src/devices/bus/ti99_peb/samsmem.cpp @@ -0,0 +1,133 @@ +// license:LGPL-2.1+ +// copyright-holders:Michael Zapf +/**************************************************************************** + + TI-99 SuperAMS Memory Expansion Card. Uses a 74LS612 memory mapper. + The card can be equipped with up to 1 MiB of static CMOS memory; it is + not buffered, however. + + SAMS organizes memory in 4 KiB blocks which are mapped into the address + space by a memory mapper. The mapper can be configured via a sequence of + addresses at 4000, 4002, ..., 401e, which correspond to memory locations + 0000-0fff, 1000-1fff, ..., f000-ffff. + + Michael Zapf + + February 2012: Rewritten as class + +*****************************************************************************/ + +#include "samsmem.h" +#define RAMREGION "ram" + +#define SAMS_CRU_BASE 0x1e00 + +#define VERBOSE 1 +#define LOG logerror + +sams_memory_expansion_device::sams_memory_expansion_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) +: ti_expansion_card_device(mconfig, TI99_SAMSMEM, "SuperAMS memory expansion card", tag, owner, clock, "ti99_sams", __FILE__) +{ +} + +/* + Memory read. The SAMS card has two address areas: The memory is at locations + 0x2000-0x3fff and 0xa000-0xffff, and the mapper area is at 0x4000-0x401e + (only even addresses). +*/ +READ8Z_MEMBER(sams_memory_expansion_device::readz) +{ + int base = 0; + + if (m_access_mapper && ((offset & 0xe000)==0x4000)) + { + *value = m_mapper[(offset>>1)&0x000f]; + } + + if (((offset & 0xe000)==0x2000) || ((offset & 0xe000)==0xa000) || ((offset & 0xe000)==0xc000) || ((offset & 0xe000)==0xe000)) + { + if (!m_map_mode) + { + // transparent mode + *value = m_ram[offset & 0xffff]; + } + else + { + base = (m_mapper[(offset & 0xf000)>>12] << 12); + *value = m_ram[base | (offset & 0x0fff)]; + } + } +} + +WRITE8_MEMBER(sams_memory_expansion_device::write) +{ + int base = 0; + + if (m_access_mapper && ((offset & 0xe000)==0x4000)) + { + m_mapper[(offset>>1)&0x000f] = data; + } + + if (((offset & 0xe000)==0x2000) || ((offset & 0xe000)==0xa000) || ((offset & 0xe000)==0xc000) || ((offset & 0xe000)==0xe000)) + { + if (!m_map_mode) + { + // transparent mode + m_ram[offset & 0xffff] = data; + } + else + { + base = (m_mapper[(offset & 0xf000)>>12] << 12); + m_ram[base | (offset & 0x0fff)] = data; + } + } +} + +/* + CRU read. None here. +*/ +READ8Z_MEMBER(sams_memory_expansion_device::crureadz) +{ +} + +/* + CRU write. Turns on the mapper and allows to change it. +*/ +WRITE8_MEMBER(sams_memory_expansion_device::cruwrite) +{ + if ((offset & 0xff00)==SAMS_CRU_BASE) + { + if (VERBOSE>7) LOG("cru address %04x = %02x\n", offset&0xffff, data); + + if ((offset & 0x000e)==0) m_access_mapper = (data!=0); + if ((offset & 0x000e)==2) m_map_mode = (data!=0); + } +} + + +ROM_START( sams_card ) + ROM_REGION(0x100000, RAMREGION, 0) + ROM_FILL(0x0000, 0x100000, 0x00) +ROM_END + +void sams_memory_expansion_device::device_start() +{ + if (VERBOSE>5) LOG("SuperAMS: start\n"); + m_ram = memregion(RAMREGION)->base(); +} + +void sams_memory_expansion_device::device_reset() +{ + if (VERBOSE>5) LOG("SuperAMS: reset\n"); + // Resetting values + m_map_mode = false; + m_access_mapper = false; + for (int i=0; i < 16; i++) m_mapper[i] = 0; +} + +const rom_entry *sams_memory_expansion_device::device_rom_region() const +{ + return ROM_NAME( sams_card ); +} + +const device_type TI99_SAMSMEM = &device_creator<sams_memory_expansion_device>; |