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z80/z80.cpp: Cleaned up unnecessary internal state validation (SA_BUSACK) which caused INT skip #14294

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Merged
merged 1 commit into from
Oct 9, 2025
+14 −16
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z80/z80.cpp: Cleaned up unnecessary internal state validation (SA_BUSACK) which caused INT skip #14294

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6 changes: 2 additions & 4 deletions src/devices/cpu/z80/z80.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -789,11 +789,9 @@ void z80_device::execute_set_input(int inputnum, int state)
switch (inputnum)
{
case Z80_INPUT_LINE_BUSRQ:
m_busrq_state = state;
if (state != CLEAR_LINE)
if (m_busrq_state == CLEAR_LINE && state != CLEAR_LINE)
set_service_attention<SA_BUSRQ, 1>();
else
set_service_attention<SA_BUSRQ, 0>();
m_busrq_state = state;
break;

case INPUT_LINE_NMI:
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13 changes: 6 additions & 7 deletions src/devices/cpu/z80/z80.h
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Original file line number Diff line number Diff line change
Expand Up @@ -140,13 +140,12 @@ class z80_device : public cpu_device, public z80_daisy_chain_interface
devcb_write_line m_busack_cb;

static constexpr u8 SA_BUSRQ = 0;
static constexpr u8 SA_BUSACK = 1;
static constexpr u8 SA_NMI_PENDING = 2;
static constexpr u8 SA_IRQ_ON = 3;
static constexpr u8 SA_HALT = 4;
static constexpr u8 SA_AFTER_EI = 5;
static constexpr u8 SA_AFTER_LDAIR = 6;
static constexpr u8 SA_NSC800_IRQ_ON = 7;
static constexpr u8 SA_NMI_PENDING = 1;
static constexpr u8 SA_IRQ_ON = 2;
static constexpr u8 SA_HALT = 3;
static constexpr u8 SA_AFTER_EI = 4;
static constexpr u8 SA_AFTER_LDAIR = 5;
static constexpr u8 SA_NSC800_IRQ_ON = 6;
u8 m_service_attention; // bitmap for required handling in service step

PAIR16 m_prvpc;
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11 changes: 6 additions & 5 deletions src/devices/cpu/z80/z80.lst
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Original file line number Diff line number Diff line change
Expand Up @@ -1048,17 +1048,18 @@ ffff
if (m_busrq_state) { // SA_BUSRQ
if (!m_busack_state) {
m_busack_state = 1;
set_service_attention<SA_BUSACK, 1>();
m_busack_cb(1);
}
if (m_icount > 0)
m_icount = 0;
m_ref = 0xffff00;
return;
} else if (m_busack_state) { // SA_BUSACK
m_busack_state = 0;
set_service_attention<SA_BUSACK, 0>();
m_busack_cb(0);
} else {
set_service_attention<SA_BUSRQ, 0>();
if (m_busack_state) {
m_busack_state = 0;
m_busack_cb(0);
}
}
@check_interrupts
set_service_attention<SA_AFTER_EI, 0>();
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