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/* |
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* CPUC64_SC.cpp - Single-cycle 6510 (C64) emulation |
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* |
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* Frodo (C) 1994-1997,2002-2005 Christian Bauer |
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* Frodo Copyright (C) Christian Bauer |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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dfff_byte = 0x55; |
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BALow = false; |
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first_irq_cycle = first_nmi_cycle = 0; |
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opflags = 0; |
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} |
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ddr = s->ddr; |
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pr = s->pr; |
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pr_out = 0; // FIXME: should be saved in MOS6510State |
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new_config(); |
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pc = s->pc; |
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void MOS6510::new_config(void) |
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{ |
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uint8 port = ~ddr | pr; |
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pr_out = (pr_out & ~ddr) | (pr & ddr); |
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uint8 port = pr | ~ddr; |
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basic_in = (port & 3) == 3; |
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kernal_in = port & 2; |
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uint8 MOS6510::read_byte(uint16 adr) |
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{ |
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if (adr < 0xa000) { |
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if (adr >= 2) |
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if (adr >= 2) { |
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return ram[adr]; |
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else if (adr == 0) |
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} else if (adr == 0) { |
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return ddr; |
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else |
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return (ddr & pr) | (~ddr & 0x17); |
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} else { |
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uint8 byte = (pr | ~ddr) & (pr_out | 0x17); |
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if (!(ddr & 0x20)) |
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byte &= 0xdf; |
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return byte; |
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} |
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} else |
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return read_byte_io(adr); |
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} |
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* $dfa0-$dfff: Emulator identification |
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*/ |
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< |
const char frodo_id[0x5c] = "FRODO\r(C) 1994-1997 CHRISTIAN BAUER"; |
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const char frodo_id[0x5c] = "FRODO\r(C) CHRISTIAN BAUER"; |
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uint8 MOS6510::read_emulator_id(uint16 adr) |
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{ |
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ram[0x8004] = 0; |
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// Initialize extra 6510 registers and memory configuration |
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ddr = pr = 0; |
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ddr = pr = pr_out = 0; |
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new_config(); |
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// Clear all interrupt lines |
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interrupt.intr_any = 0; |
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nmi_state = false; |
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opflags = 0; |
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// Read reset vector |
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pc = read_word(0xfffc); |
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// Any pending interrupts in state 0 (opcode fetch)? |
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if (!state && interrupt.intr_any) { |
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if (interrupt.intr[INT_RESET]) |
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if (interrupt.intr[INT_RESET]) { |
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Reset(); |
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else if (interrupt.intr[INT_NMI] && (the_c64->CycleCounter-first_nmi_cycle >= 2)) { |
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interrupt.intr[INT_NMI] = false; // Simulate an edge-triggered input |
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state = 0x0010; |
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} else if ((interrupt.intr[INT_VICIRQ] || interrupt.intr[INT_CIAIRQ]) && (the_c64->CycleCounter-first_irq_cycle >= 2) && !i_flag) |
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state = 0x0008; |
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} else if (interrupt.intr[INT_NMI]) { |
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uint32 int_delay = (opflags & OPFLAG_INT_DELAYED) ? 1 : 0; // Taken branches to the same page delay the NMI |
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if (the_c64->CycleCounter - first_nmi_cycle - int_delay >= 2) { |
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interrupt.intr[INT_NMI] = false; // Simulate an edge-triggered input |
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state = 0x0010; |
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opflags = 0; |
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} |
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} else if ((interrupt.intr[INT_VICIRQ] || interrupt.intr[INT_CIAIRQ]) && |
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(!i_flag || (opflags & OPFLAG_IRQ_DISABLED)) && !(opflags & OPFLAG_IRQ_ENABLED)) { |
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uint32 int_delay = (opflags & OPFLAG_INT_DELAYED) ? 1 : 0; // Taken branches to the same page delay the IRQ |
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if (the_c64->CycleCounter - first_irq_cycle - int_delay >= 2) { |
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state = 0x0008; |
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opflags = 0; |
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} |
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} |
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} |
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#include "CPU_emulcycle.h" |
