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

Author: holub

src/devices/cpu/z80/z80.cpp

@@ -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:

src/devices/cpu/z80/z80.h

@@ -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;

src/devices/cpu/z80/z80.lst

@@ -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>();