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cebix |
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/* |
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* CPU1541.h - 6502 (1541) emulation (line based) |
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* |
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cebix |
1.5 |
* Frodo Copyright (C) Christian Bauer |
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cebix |
1.1 |
* |
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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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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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#ifndef _CPU_1541_H |
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#define _CPU_1541_H |
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#include "CIA.h" |
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#include "C64.h" |
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// Set this to 1 if the 6502 PC should be represented by a real pointer |
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#ifndef FRODO_SC |
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#ifndef PC_IS_POINTER |
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#define PC_IS_POINTER 1 |
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#endif |
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#endif |
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// Set this to 1 for more precise CPU cycle calculation |
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#ifndef PRECISE_CPU_CYCLES |
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#define PRECISE_CPU_CYCLES 0 |
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#endif |
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// Interrupt types |
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enum { |
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INT_VIA1IRQ, |
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INT_VIA2IRQ, |
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INT_IECIRQ |
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// INT_RESET (private) |
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}; |
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class C64; |
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class Job1541; |
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class C64Display; |
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struct MOS6502State; |
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// 6502 emulation (1541) |
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class MOS6502_1541 { |
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public: |
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MOS6502_1541(C64 *c64, Job1541 *job, C64Display *disp, uint8 *Ram, uint8 *Rom); |
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#ifdef FRODO_SC |
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void EmulateCycle(void); // Emulate one clock cycle |
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#else |
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int EmulateLine(int cycles_left); // Emulate until cycles_left underflows |
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#endif |
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void Reset(void); |
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void AsyncReset(void); // Reset the CPU asynchronously |
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void GetState(MOS6502State *s); |
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void SetState(MOS6502State *s); |
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uint8 ExtReadByte(uint16 adr); |
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void ExtWriteByte(uint16 adr, uint8 byte); |
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void CountVIATimers(int cycles); |
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void NewATNState(void); |
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void IECInterrupt(void); |
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void TriggerJobIRQ(void); |
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bool InterruptEnabled(void); |
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MOS6526_2 *TheCIA2; // Pointer to C64 CIA 2 |
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uint8 IECLines; // State of IEC lines (bit 7 - DATA, bit 6 - CLK) |
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bool Idle; // true: 1541 is idle |
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private: |
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uint8 read_byte(uint16 adr); |
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uint8 read_byte_io(uint16 adr); |
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uint16 read_word(uint16 adr); |
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void write_byte(uint16 adr, uint8 byte); |
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void write_byte_io(uint16 adr, uint8 byte); |
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uint8 read_zp(uint16 adr); |
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uint16 read_zp_word(uint16 adr); |
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void write_zp(uint16 adr, uint8 byte); |
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void jump(uint16 adr); |
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void illegal_op(uint8 op, uint16 at); |
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void illegal_jump(uint16 at, uint16 to); |
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void do_adc(uint8 byte); |
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void do_sbc(uint8 byte); |
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uint8 *ram; // Pointer to main RAM |
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uint8 *rom; // Pointer to ROM |
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C64 *the_c64; // Pointer to C64 object |
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C64Display *the_display; // Pointer to C64 display object |
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Job1541 *the_job; // Pointer to 1541 job object |
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union { // Pending interrupts |
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uint8 intr[4]; // Index: See definitions above |
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unsigned long intr_any; |
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} interrupt; |
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uint8 n_flag, z_flag; |
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bool v_flag, d_flag, i_flag, c_flag; |
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uint8 a, x, y, sp; |
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#if PC_IS_POINTER |
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uint8 *pc, *pc_base; |
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#else |
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uint16 pc; |
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#endif |
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#ifdef FRODO_SC |
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uint32 first_irq_cycle; |
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cebix |
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enum { |
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OPFLAG_IRQ_DISABLED = 0x01, |
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OPFLAG_IRQ_ENABLED = 0x02, |
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OPFLAG_INT_DELAYED = 0x04 |
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}; |
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uint8 opflags; // Interrupt operation flags |
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uint8 state, op; // Current state and opcode |
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uint16 ar, ar2; // Address registers |
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uint8 rdbuf; // Data buffer for RMW instructions |
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uint8 ddr, pr; // Processor port |
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#else |
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int borrowed_cycles; // Borrowed cycles from next line |
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#endif |
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uint8 via1_pra; // PRA of VIA 1 |
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uint8 via1_ddra; // DDRA of VIA 1 |
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uint8 via1_prb; // PRB of VIA 1 |
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uint8 via1_ddrb; // DDRB of VIA 1 |
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uint16 via1_t1c; // T1 Counter of VIA 1 |
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uint16 via1_t1l; // T1 Latch of VIA 1 |
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uint16 via1_t2c; // T2 Counter of VIA 1 |
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uint16 via1_t2l; // T2 Latch of VIA 1 |
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uint8 via1_sr; // SR of VIA 1 |
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uint8 via1_acr; // ACR of VIA 1 |
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uint8 via1_pcr; // PCR of VIA 1 |
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uint8 via1_ifr; // IFR of VIA 1 |
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uint8 via1_ier; // IER of VIA 1 |
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uint8 via2_pra; // PRA of VIA 2 |
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uint8 via2_ddra; // DDRA of VIA 2 |
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uint8 via2_prb; // PRB of VIA 2 |
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uint8 via2_ddrb; // DDRB of VIA 2 |
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uint16 via2_t1c; // T1 Counter of VIA 2 |
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uint16 via2_t1l; // T1 Latch of VIA 2 |
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uint16 via2_t2c; // T2 Counter of VIA 2 |
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uint16 via2_t2l; // T2 Latch of VIA 2 |
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uint8 via2_sr; // SR of VIA 2 |
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uint8 via2_acr; // ACR of VIA 2 |
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uint8 via2_pcr; // PCR of VIA 2 |
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uint8 via2_ifr; // IFR of VIA 2 |
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uint8 via2_ier; // IER of VIA 2 |
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}; |
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// 6502 state |
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struct MOS6502State { |
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uint8 a, x, y; |
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uint8 p; // Processor flags |
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uint16 pc, sp; |
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uint8 intr[4]; // Interrupt state |
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bool instruction_complete; |
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bool idle; |
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uint8 via1_pra; // VIA 1 |
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uint8 via1_ddra; |
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uint8 via1_prb; |
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uint8 via1_ddrb; |
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uint16 via1_t1c; |
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uint16 via1_t1l; |
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uint16 via1_t2c; |
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uint16 via1_t2l; |
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uint8 via1_sr; |
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uint8 via1_acr; |
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uint8 via1_pcr; |
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uint8 via1_ifr; |
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uint8 via1_ier; |
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uint8 via2_pra; // VIA 2 |
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uint8 via2_ddra; |
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uint8 via2_prb; |
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uint8 via2_ddrb; |
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uint16 via2_t1c; |
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uint16 via2_t1l; |
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uint16 via2_t2c; |
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uint16 via2_t2l; |
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uint8 via2_sr; |
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uint8 via2_acr; |
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uint8 via2_pcr; |
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uint8 via2_ifr; |
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uint8 via2_ier; |
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}; |
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/* |
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* Trigger job loop IRQ |
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*/ |
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#ifdef FRODO_SC |
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inline void MOS6502_1541::TriggerJobIRQ(void) |
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{ |
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if (!(interrupt.intr[INT_VIA2IRQ])) |
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first_irq_cycle = the_c64->CycleCounter; |
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interrupt.intr[INT_VIA2IRQ] = true; |
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Idle = false; |
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} |
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#else |
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inline void MOS6502_1541::TriggerJobIRQ(void) |
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{ |
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interrupt.intr[INT_VIA2IRQ] = true; |
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Idle = false; |
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} |
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#endif |
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/* |
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* Count VIA timers |
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*/ |
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inline void MOS6502_1541::CountVIATimers(int cycles) |
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{ |
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unsigned long tmp; |
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via1_t1c = tmp = via1_t1c - cycles; |
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if (tmp > 0xffff) { |
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if (via1_acr & 0x40) // Reload from latch in free-run mode |
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via1_t1c = via1_t1l; |
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via1_ifr |= 0x40; |
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} |
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if (!(via1_acr & 0x20)) { // Only count in one-shot mode |
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via1_t2c = tmp = via1_t2c - cycles; |
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if (tmp > 0xffff) |
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via1_ifr |= 0x20; |
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} |
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via2_t1c = tmp = via2_t1c - cycles; |
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if (tmp > 0xffff) { |
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if (via2_acr & 0x40) // Reload from latch in free-run mode |
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via2_t1c = via2_t1l; |
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via2_ifr |= 0x40; |
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if (via2_ier & 0x40) |
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TriggerJobIRQ(); |
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} |
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if (!(via2_acr & 0x20)) { // Only count in one-shot mode |
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via2_t2c = tmp = via2_t2c - cycles; |
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if (tmp > 0xffff) |
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via2_ifr |= 0x20; |
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} |
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} |
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/* |
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* ATN line probably changed state, recalc IECLines |
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*/ |
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inline void MOS6502_1541::NewATNState(void) |
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{ |
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uint8 byte = ~via1_prb & via1_ddrb; |
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IECLines = (byte << 6) & ((~byte ^ TheCIA2->IECLines) << 3) & 0x80 // DATA (incl. ATN acknowledge) |
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| (byte << 3) & 0x40; // CLK |
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} |
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/* |
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* Interrupt by negative edge of ATN on IEC bus |
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*/ |
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inline void MOS6502_1541::IECInterrupt(void) |
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{ |
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ram[0x7c] = 1; |
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// Wake up 1541 |
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Idle = false; |
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} |
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/* |
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* Test if interrupts are enabled (for job loop) |
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*/ |
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inline bool MOS6502_1541::InterruptEnabled(void) |
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{ |
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return !i_flag; |
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} |
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#endif |
