99 lines
2.4 KiB
C
99 lines
2.4 KiB
C
/* FCE Ultra - NES/Famicom Emulator
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*
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* Copyright notice for this file:
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* Copyright (C) 2025 NewRisingSun
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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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* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "mapinc.h"
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#include "vrc2and4.h"
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static uint8 clockMode;
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static uint8 pending;
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static uint8 counter1;
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static uint8 counter2;
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static uint8 prescaler;
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static SFORMAT Mapper222_stateRegs[] ={
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{ &clockMode, 1, "CLKM" },
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{ &pending, 1, "PEND" },
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{ &counter1, 1, "CNT1" },
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{ &counter2, 1, "CNT2" },
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{ &prescaler, 1, "PRES" },
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{ 0 }
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};
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static void sync () {
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VRC24_syncPRG(0x01F, 0x000);
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VRC24_syncCHR(0x1FF, 0x000);
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VRC24_syncMirror();
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}
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DECLFW(Mapper222_nibblizeCHR) {
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if (~A &1) {
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VRC24_writeReg(A, V);
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VRC24_writeReg(A |1, V >>4);
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}
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}
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DECLFW(Mapper222_writeIRQ) {
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switch(A &3) {
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case 0: clockMode =0;
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break;
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case 1: pending =false;
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if (!clockMode) {
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counter1 =V &0xF;
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counter2 =V >>4;
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}
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break;
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case 2: clockMode =1;
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break;
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}
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}
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void FP_FASTAPASS(1) Mapper222_cpuCycle(int a) {
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while (a--) {
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uint8 previousPrescaler =prescaler;
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if (pending)
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prescaler =0;
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else
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prescaler++;
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if (clockMode && ~previousPrescaler &0x40 && prescaler &0x40) {
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if (++counter1 ==0xF && ++counter2 ==0xF) pending =1;
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counter1 &=0xF;
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counter2 &=0xF;
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}
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if (pending)
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X6502_IRQBegin(FCEU_IQEXT);
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else
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X6502_IRQEnd(FCEU_IQEXT);
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}
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}
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void Mapper222_power(void) {
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clockMode =pending =counter1 =counter2 =prescaler =0;
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VRC24_power();
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SetWriteHandler(0xB000, 0xEFFF, Mapper222_nibblizeCHR);
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SetWriteHandler(0xF000, 0xFFFF, Mapper222_writeIRQ);
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}
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void Mapper222_Init (CartInfo *info) {
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VRC24_init(info, sync, 0x01, 0x02, 0, 0, 0);
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AddExState(Mapper222_stateRegs, ~0, 0, 0);
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info->Power =Mapper222_power;
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MapIRQHook =Mapper222_cpuCycle;
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}
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