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Accurate byte-smearing write behavior for 32-bit members of the M68K family

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This commit is contained in:
AJR 2019-06-06 18:15:56 -04:00
parent 66a1d65545
commit c4843c23bc
1 changed files with 48 additions and 3 deletions
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51
src/devices/cpu/m68000/m68kcpu.cpp
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@ -1342,6 +1342,10 @@ void m68000_base_device::init16(address_space &space, address_space &ospace)
* 32-bit data memory interface
****************************************************************************/
static inline u32 dword_from_byte(u8 data) { return u32(data) << 24 | u32(data) << 16 | u32(data) << 8 | data; }
static inline u32 dword_from_word(u16 data) { return u32(data) << 16 | data; }
static inline u32 dword_from_unaligned_word(u16 data) { return u32(data & 0xff00) << 16 | u32(data) << 8 | (data & 0xff00) >> 8; }
/* interface for 32-bit data bus (68EC020, 68020) */
void m68000_base_device::init32(address_space &space, address_space &ospace)
{
@ -1353,10 +1357,51 @@ void m68000_base_device::init32(address_space &space, address_space &ospace)
m_read8 = [this](offs_t address) -> u8 { return m_space->read_byte(address); };
m_read16 = [this](offs_t address) -> u16 { return m_space->read_word_unaligned(address); };
m_read32 = [this](offs_t address) -> u32 { return m_space->read_dword_unaligned(address); };
m_write8 = [this](offs_t address, u8 data) { m_space->write_byte(address, data); };
m_write16 = [this](offs_t address, u16 data) { m_space->write_word_unaligned(address, data); };
m_write32 = [this](offs_t address, u32 data) { m_space->write_dword_unaligned(address, data); };
m_write8 = [this](offs_t address, u8 data) {
m_space->write_dword(address & 0xfffffffcU, dword_from_byte(data), 0xff000000U >> 8 * (address & 3));
};
m_write16 = [this](offs_t address, u16 data) {
switch (address & 3) {
case 0:
m_space->write_dword(address, dword_from_word(data), 0xffff0000U);
break;
case 1:
m_space->write_dword(address - 1, dword_from_unaligned_word(data), 0x00ffff00);
break;
case 2:
m_space->write_dword(address - 2, dword_from_word(data), 0x0000ffff);
break;
case 3:
m_space->write_dword(address - 3, dword_from_unaligned_word(data), 0x000000ff);
m_space->write_dword(address + 1, dword_from_byte(data & 0x00ff), 0xff000000);
break;
}
};
m_write32 = [this](offs_t address, u32 data) {
switch (address & 3) {
case 0:
m_space->write_dword(address, data, 0xffffffffU);
break;
case 1:
m_space->write_dword(address - 1, (data & 0xff000000U) | (data & 0xffffff00U) >> 8, 0x00ffffff);
m_space->write_dword(address + 3, dword_from_byte(data & 0x000000ff), 0xff000000U);
break;
case 2:
m_space->write_dword(address - 2, dword_from_word((data & 0xffff0000U) >> 16), 0x0000ffff);
m_space->write_dword(address + 2, dword_from_word(data & 0x0000ffff), 0xffff0000U);
break;
case 3:
m_space->write_dword(address - 3, dword_from_unaligned_word((data & 0xffff0000U) >> 16), 0x000000ff);
m_space->write_dword(address + 1, (data & 0x00ffffff) << 8 | (data & 0xff000000U) >> 24, 0xffffff00U);
break;
}
};
}
/* interface for 32-bit data bus with PMMU */