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t11: handle unaligned accesses to I/O page. #14347

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Merged
merged 1 commit into from
Oct 22, 2025
+32 −2
Merged

t11: handle unaligned accesses to I/O page. #14347

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30 changes: 28 additions & 2 deletions src/devices/cpu/t11/t11.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -138,13 +138,39 @@ void t11_device::WBYTE(int addr, int data)

int t11_device::RWORD(int addr)
{
return m_program.read_word(addr & 0xfffe);
if (addr < 0160000)
return m_program.read_word(addr & 0xfffe);
else // accessing I/O page
{
auto flags = m_program.lookup_read_word_flags(addr);
if (!flags)
return m_program.read_word(addr & 0xfffe);
else if (flags & UNALIGNED_WORD)
return m_program.read_word_unaligned(addr);
else if (flags & UNALIGNED_BYTE)
return m_program.read_byte(addr);
Comment on lines +150 to +151
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@cuavas cuavas Oct 30, 2025

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Does this path actually work? It looks like it causes it to always do a byte access, even if the address is word-aligned.

else
return m_program.read_word(addr & 0xfffe);
}
}


void t11_device::WWORD(int addr, int data)
{
m_program.write_word(addr & 0xfffe, data);
if (addr < 0160000)
m_program.write_word(addr & 0xfffe, data);
else // accessing I/O page
{
auto flags = m_program.lookup_write_word_flags(addr);
if (!flags)
m_program.write_word(addr & 0xfffe, data);
else if (flags & UNALIGNED_WORD)
m_program.write_word_unaligned(addr, data);
else if (flags & UNALIGNED_BYTE)
m_program.write_byte(addr, data);
else
m_program.write_word(addr & 0xfffe, data);
}
}


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4 changes: 4 additions & 0 deletions src/devices/cpu/t11/t11.h
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,10 @@ class t11_device : public cpu_device
static constexpr uint8_t POWER_FAIL = PF_LINE;
static constexpr uint8_t BUS_ERROR = 8;

// memory flags
static constexpr uint16_t UNALIGNED_BYTE = 1;
static constexpr uint16_t UNALIGNED_WORD = 2;

// construction/destruction
t11_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);

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