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lwriter.cpp: Reimplement the 0x600000-0x7fffff range to bitwise-OR on write. Fixes GitHub issue #8309.

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Jeff Muizelaar 2021-07-19 19:13:02 -04:00 committed by GitHub
parent 13e9acd192
commit 0c20873355
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1 changed files with 16 additions and 5 deletions
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21
src/mame/drivers/lwriter.cpp
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@ -111,6 +111,9 @@ public:
, m_scc(*this, "scc")
, m_via(*this, "via")
, m_dsw1(*this, "DSW1")
, m_dram_ptr(*this, "dram")
, m_sram_ptr(*this, "sram")
, m_rom_ptr(*this, "rom")
, m_overlay(1)
, m_via_pb(0)
, m_print_sc(1)
@ -129,6 +132,7 @@ private:
void bankedarea_w(offs_t offset, uint16_t data, uint16_t mem_mask = ~0);
uint8_t eeprom_r(offs_t offset);
void eeprom_w(offs_t offset, uint8_t data, uint8_t mem_mask = ~0);
void dram_or_w(offs_t offset, uint16_t data, uint16_t mem_mask = ~0);
void led_out_w(uint8_t data);
void fifo_out_w(uint8_t data);
uint8_t via_pa_r();
@ -150,7 +154,8 @@ private:
required_device<via6522_device> m_via;
required_ioport m_dsw1;
uint16_t *m_dram_ptr, *m_sram_ptr, *m_rom_ptr;
required_shared_ptr<uint16_t> m_dram_ptr;
required_region_ptr<uint16_t> m_sram_ptr, m_rom_ptr;
bool m_overlay;
uint8_t m_via_pb;
bool m_print_sc;
@ -225,7 +230,11 @@ void lwriter_state::maincpu_map(address_map &map)
map(0x000000, 0x1fffff).rw(FUNC(lwriter_state::bankedarea_r), FUNC(lwriter_state::bankedarea_w));
map(0x200000, 0x2fffff).rom().region("rom", 0); // 1MB ROM
//map(0x300000, 0x3fffff) // open bus?
map(0x400000, 0x5fffff).ram().share("dram").mirror(0x200000); // 2MB DRAM
map(0x400000, 0x5fffff).ram().share("dram"); // 2MB DRAM
// DRAM appears to mirrored through 0x600000 but when written to does a bitwise-or with the existing data
// instead of replacing it. This presumeably improves the performance of these operations by avoiding
// an extra memory read.
map(0x600000, 0x7fffff).readonly().share("dram").w(FUNC(lwriter_state::dram_or_w));
map(0x800000, 0x800000).w(FUNC(lwriter_state::led_out_w)).mirror(0x1ffffe); // mirror is a guess given that the pals can only decode A18-A23
map(0x800001, 0x800001).w(FUNC(lwriter_state::fifo_out_w)).mirror(0x1ffffe); // mirror is a guess given that the pals can only decode A18-A23
map(0xc00001, 0xc00001).w(m_scc, FUNC(scc8530_device::cb_w)).mirror(0x1ffff8);
@ -262,9 +271,6 @@ INPUT_PORTS_END
/* Start it up */
void lwriter_state::machine_start()
{
m_rom_ptr = (uint16_t*)memregion("rom")->base();
m_dram_ptr = (uint16_t*)memshare("dram")->ptr();
m_sram_ptr = (uint16_t*)memregion("sram")->base();
// do stuff here later on like setting up printer mechanisms HLE timers etc
}
@ -306,6 +312,11 @@ void lwriter_state::bankedarea_w(offs_t offset, uint16_t data, uint16_t mem_mask
if(!machine().side_effects_disabled()) { logerror("Attempt to write banked area (with overlay off) with data %04X to offset %08X IGNORED!\n", data, offset<<1); }
}
void lwriter_state::dram_or_w(offs_t offset, uint16_t data, uint16_t mem_mask)
{
m_dram_ptr[offset] |= ((m_dram_ptr[offset] & ~mem_mask) | (data & mem_mask));
}
uint8_t lwriter_state::eeprom_r(offs_t offset)
{
uint8_t result = 0;