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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 |
1.2 |
* Frodo (C) 1994-1997,2002-2003 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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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
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