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i8085: small cleanup
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hap
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8f2cde3399
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@ -108,7 +108,7 @@
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* April 2025, Roberto Fresca
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* - Reworked the DSUB (Double Substraction) undocumented instruction.
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* - Reworked the RDEL (Rotate D and E Left with Carry) undocumented instruction.
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* (ref: https://robertofresca.com/files/New_8085_instruction.pdf)
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* (ref: https://robertofresca.com/files/New_8085_instruction.pdf)
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*
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*****************************************************************************/
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@ -274,10 +274,10 @@ void i8085a_cpu_device::init_tables()
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{
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for (int i = 0; i < 256; i++)
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{
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/* cycles */
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// cycles
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lut_cycles[i] = is_8085() ? lut_cycles_8085[i] : lut_cycles_8080[i];
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/* flags */
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// flags
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u8 zs = 0;
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if (i == 0) zs |= ZF;
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if (i & 0x80) zs |= SF;
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@ -312,7 +312,7 @@ void i8085a_cpu_device::device_start()
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init_tables();
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/* set up the state table */
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// set up the state table
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state_add(I8085_PC, "PC", m_PC.w.l);
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state_add(STATE_GENPC, "GENPC", m_PC.w.l).noshow();
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state_add(STATE_GENPCBASE, "CURPC", m_PC.w.l).noshow();
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@ -347,7 +347,7 @@ void i8085a_cpu_device::device_start()
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space(has_space(AS_OPCODES) ? AS_OPCODES : AS_PROGRAM).cache(m_copcodes);
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space(AS_IO).specific(m_io);
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/* register for state saving */
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// register for state saving
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save_item(NAME(m_PC.w.l));
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save_item(NAME(m_SP.w.l));
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save_item(NAME(m_AF.w.l));
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@ -485,7 +485,7 @@ void i8085a_cpu_device::execute_set_input(int irqline, int state)
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{
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int newstate = (state != CLEAR_LINE);
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/* TRAP is level and edge-triggered NMI */
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// TRAP is level and edge-triggered NMI
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if (irqline == I8085_TRAP_LINE)
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{
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if (!m_nmi_state && newstate)
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@ -495,7 +495,7 @@ void i8085a_cpu_device::execute_set_input(int irqline, int state)
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m_nmi_state = newstate;
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}
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/* RST7.5 is edge-triggered */
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// RST7.5 is edge-triggered
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else if (irqline == I8085_RST75_LINE)
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{
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if (!m_irq_state[I8085_RST75_LINE] && newstate)
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@ -503,105 +503,105 @@ void i8085a_cpu_device::execute_set_input(int irqline, int state)
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m_irq_state[I8085_RST75_LINE] = newstate;
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}
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/* remaining sources are level triggered */
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// remaining sources are level triggered
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else if (irqline < std::size(m_irq_state))
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m_irq_state[irqline] = state;
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}
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void i8085a_cpu_device::break_halt_for_interrupt()
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{
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/* de-halt if necessary */
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// de-halt if necessary
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if (m_halt)
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{
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m_PC.w.l++;
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m_halt = 0;
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set_status(0x26); /* int ack while halt */
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set_status(0x26); // int ack while halt
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}
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else
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set_status(0x23); /* int ack */
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set_status(0x23); // int ack
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m_in_acknowledge = true;
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}
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void i8085a_cpu_device::check_for_interrupts()
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{
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/* TRAP is the highest priority */
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// TRAP is the highest priority
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if (m_trap_pending)
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{
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/* the first RIM after a TRAP reflects the original IE state; remember it here,
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setting the high bit to indicate it is valid */
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// the first RIM after a TRAP reflects the original IE state; remember it here,
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// setting the high bit to indicate it is valid
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m_trap_im_copy = m_im | 0x80;
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/* reset the pending state */
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// reset the pending state
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m_trap_pending = false;
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/* break out of HALT state and call the IRQ ack callback */
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// break out of HALT state and call the IRQ ack callback
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break_halt_for_interrupt();
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standard_irq_callback(I8085_TRAP_LINE, m_PC.w.l);
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/* push the PC and jump to $0024 */
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// push the PC and jump to $0024
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op_push(m_PC);
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set_inte(0);
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m_PC.w.l = ADDR_TRAP;
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m_icount -= 11;
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}
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/* followed by RST7.5 */
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// followed by RST7.5
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else if ((m_im & IM_I75) && !(m_im & IM_M75) && (m_im & IM_IE))
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{
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/* reset the pending state (which is CPU-visible via the RIM instruction) */
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// reset the pending state (which is CPU-visible via the RIM instruction)
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m_im &= ~IM_I75;
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/* break out of HALT state and call the IRQ ack callback */
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// break out of HALT state and call the IRQ ack callback
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break_halt_for_interrupt();
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standard_irq_callback(I8085_RST75_LINE, m_PC.w.l);
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/* push the PC and jump to $003C */
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// push the PC and jump to $003C
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op_push(m_PC);
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set_inte(0);
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m_PC.w.l = ADDR_RST75;
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m_icount -= 11;
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}
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/* followed by RST6.5 */
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// followed by RST6.5
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else if (m_irq_state[I8085_RST65_LINE] && !(m_im & IM_M65) && (m_im & IM_IE))
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{
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/* break out of HALT state and call the IRQ ack callback */
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// break out of HALT state and call the IRQ ack callback
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break_halt_for_interrupt();
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standard_irq_callback(I8085_RST65_LINE, m_PC.w.l);
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/* push the PC and jump to $0034 */
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// push the PC and jump to $0034
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op_push(m_PC);
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set_inte(0);
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m_PC.w.l = ADDR_RST65;
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m_icount -= 11;
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}
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/* followed by RST5.5 */
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// followed by RST5.5
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else if (m_irq_state[I8085_RST55_LINE] && !(m_im & IM_M55) && (m_im & IM_IE))
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{
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/* break out of HALT state and call the IRQ ack callback */
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// break out of HALT state and call the IRQ ack callback
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break_halt_for_interrupt();
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standard_irq_callback(I8085_RST55_LINE, m_PC.w.l);
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/* push the PC and jump to $002C */
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// push the PC and jump to $002C
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op_push(m_PC);
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set_inte(0);
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m_PC.w.l = ADDR_RST55;
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m_icount -= 11;
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}
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/* followed by classic INTR */
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// followed by classic INTR
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else if (m_irq_state[I8085_INTR_LINE] && (m_im & IM_IE))
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{
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/* break out of HALT state and call the IRQ ack callback */
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// break out of HALT state and call the IRQ ack callback
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if (!m_in_inta_func.isunset())
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standard_irq_callback(I8085_INTR_LINE, m_PC.w.l);
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break_halt_for_interrupt();
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u8 vector = read_inta();
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/* use the resulting vector as an opcode to execute */
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// use the resulting vector as an opcode to execute
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set_inte(0);
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LOG("i8085 take int $%02x\n", vector);
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execute_one(vector);
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@ -654,12 +654,12 @@ u8 i8085a_cpu_device::get_rim_value()
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u8 result = m_im;
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int sid = m_in_sid_func();
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/* copy live RST5.5 and RST6.5 states */
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// copy live RST5.5 and RST6.5 states
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result &= ~(IM_I65 | IM_I55);
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if (m_irq_state[I8085_RST65_LINE]) result |= IM_I65;
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if (m_irq_state[I8085_RST55_LINE]) result |= IM_I55;
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/* fetch the SID bit if we have a callback */
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// fetch the SID bit if we have a callback
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result = (result & ~IM_SID) | (sid ? IM_SID : 0);
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return result;
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@ -867,21 +867,21 @@ void i8085a_cpu_device::op_rst(u8 v)
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void i8085a_cpu_device::execute_run()
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{
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/* check for TRAPs before diving in (can't do others because of after_ei) */
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// check for TRAPs before diving in (can't do others because of after_ei)
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if (m_trap_pending || m_after_ei == 0)
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check_for_interrupts();
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do
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{
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/* the instruction after an EI does not take an interrupt, so
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we cannot check immediately; handle post-EI behavior here */
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// the instruction after an EI does not take an interrupt, so
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// we cannot check immediately; handle post-EI behavior here
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if (m_after_ei != 0 && --m_after_ei == 0)
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check_for_interrupts();
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m_in_acknowledge = false;
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debugger_instruction_hook(m_PC.d);
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/* here we go... */
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// here we go...
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execute_one(read_op());
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} while (m_icount > 0);
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@ -926,32 +926,32 @@ void i8085a_cpu_device::execute_one(int opcode)
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break;
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case 0x08: // 8085: undocumented DSUB (Double Subtraction, HL - BC)
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if (is_8085())
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{
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// Low byte subtraction: L = L - C
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int q_low = m_HL.b.l - m_BC.b.l;
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u8 res_low = q_low & 0xff;
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// Calculate flags for low byte
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m_AF.b.l = lut_zs[res_low]
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| ((q_low >> 8) & CF) // Carry
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| ((m_HL.b.l ^ res_low ^ m_BC.b.l) & HF) // Half Carry
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| (((m_BC.b.l ^ m_HL.b.l) & (m_HL.b.l ^ res_low) & SF)) >> 5; // Overflow
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m_HL.b.l = res_low;
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if (is_8085())
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{
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// Low byte subtraction: L = L - C
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int q_low = m_HL.b.l - m_BC.b.l;
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u8 res_low = q_low & 0xff;
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// Calculate flags for low byte
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m_AF.b.l = lut_zs[res_low]
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| ((q_low >> 8) & CF) // Carry
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| ((m_HL.b.l ^ res_low ^ m_BC.b.l) & HF) // Half Carry
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| (((m_BC.b.l ^ m_HL.b.l) & (m_HL.b.l ^ res_low) & SF)) >> 5; // Overflow
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m_HL.b.l = res_low;
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// High byte subtraction: H = H - B - carry_from_low
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int q_high = m_HL.b.h - m_BC.b.h - (m_AF.b.l & CF);
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u8 res_high = q_high & 0xff;
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// Calculate flags for high byte
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m_AF.b.l = lut_zs[res_high]
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| ((q_high >> 8) & CF) // Carry
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| ((m_HL.b.h ^ res_high ^ m_BC.b.h) & HF) // Half Carry
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| (((m_BC.b.h ^ m_HL.b.h) & (m_HL.b.h ^ res_high) & SF)) >> 5; // Overflow
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m_HL.b.h = res_high;
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// High byte subtraction: H = H - B - carry_from_low
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int q_high = m_HL.b.h - m_BC.b.h - (m_AF.b.l & CF);
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u8 res_high = q_high & 0xff;
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// Calculate flags for high byte
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m_AF.b.l = lut_zs[res_high]
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| ((q_high >> 8) & CF) // Carry
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| ((m_HL.b.h ^ res_high ^ m_BC.b.h) & HF) // Half Carry
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| (((m_BC.b.h ^ m_HL.b.h) & (m_HL.b.h ^ res_high) & SF)) >> 5; // Overflow
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m_HL.b.h = res_high;
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// Set Zero flag based on 16-bit result
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m_AF.b.l = (m_AF.b.l & ~ZF) | (((m_HL.b.l | m_HL.b.h) == 0) ? ZF : 0);
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}
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break;
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// Set Zero flag based on 16-bit result
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m_AF.b.l = (m_AF.b.l & ~ZF) | (((m_HL.b.l | m_HL.b.h) == 0) ? ZF : 0);
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}
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break;
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case 0x09: // DAD B
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op_dad(m_BC.w.l);
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break;
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