MMC2Mapper.java

/*
 * HalfNES by Andrew Hoffman
 * Licensed under the GNU GPL Version 3. See LICENSE file
 */
package com.grapeshot.halfnes.mappers;

import com.grapeshot.halfnes.*;

/**
 *
 * @author Andrew
 */
public class MMC2Mapper extends Mapper {

    boolean chrlatchL = true;
    boolean chrlatchR = false;
    int chrbankL1 = 0;
    int chrbankR1 = 0;
    int chrbankL2 = 0;
    int chrbankR2 = 0;

    @Override
    public void loadrom() throws BadMapperException {
        //needs to be in every mapper. Fill with initial cfg
        super.loadrom();
        //on startup:
        for (int i = 1; i <= 32; ++i) {
            prg_map[32 - i] = prgsize - (1024 * i);
        }

        for (int i = 0; i < 8; ++i) {
            chr_map[i] = 0;
        }
    }

    @Override
    public final void cartWrite(int addr, int data) {
        if (addr < 0x8000 || addr > 0xffff) {
            super.cartWrite(addr, data);
            return;
        } else if (addr >= 0xa000 && addr <= 0xafff) {
            //remap prg
            for (int i = 0; i < 8; ++i) {
                prg_map[i] = (1024 * (i + 8 * (data & 0xf))) & (chrsize - 1);
            }
        } else if (addr >= 0xb000 && addr <= 0xbfff) {
            chrbankL1 = data & 0x1f;
            setupPPUBanks();
        } else if (addr >= 0xc000 && addr <= 0xcfff) {
            chrbankL2 = data & 0x1f;
            setupPPUBanks();
        } else if (addr >= 0xd000 && addr <= 0xdfff) {
            chrbankR1 = data & 0x1f;
            setupPPUBanks();
        } else if (addr >= 0xe000 && addr <= 0xefff) {
            chrbankR2 = data & 0x1f;
            setupPPUBanks();
        } else if (addr >= 0xf000 && addr <= 0xffff) {
            setmirroring((((data & (utils.BIT0)) != 0)) ? MirrorType.H_MIRROR : MirrorType.V_MIRROR);
        }
    }

    @Override
    public int ppuRead(final int addr) {
        int retval = super.ppuRead(addr);
        if (((addr & (utils.BIT3)) != 0)) {
            //latch fires after 2nd read from pattern table
            //A3 will be on for 2nd read b/c it's tile low bytes
            switch (addr >> 4) {
                //read of the 2nd byte of tile fd/fe/1fd/1fe
                //switches the set of character banks used for that side
                //of the pattern table
                case 0xfd:
                    if ((addr & 3) == 0) {
                        chrlatchL = false;
                        setupPPUBanks();
                    }
                    break;
                case 0xfe:
                    if ((addr & 3) == 0) {
                        chrlatchL = true;
                        setupPPUBanks();
                        break;
                    }
                case 0x1fd:
                    chrlatchR = false;
                    setupPPUBanks();
                    break;
                case 0x1fe:
                    chrlatchR = true;
                    setupPPUBanks();
                default:
                    break;
            }
        }
        return retval;
    }

//    public void notifyscanline(final int scanline) {
//        System.err.println(" ScanLine " + scanline + " " + chrlatchL);
//    }
    private void setupPPUBanks() {
        if (chrlatchL) {
            setppubank(4, 0, chrbankL2);
        } else {
            setppubank(4, 0, chrbankL1);
        }
        if (chrlatchR) {
            setppubank(4, 4, chrbankR2);
        } else {
            setppubank(4, 4, chrbankR1);
        }
    }

    private void setppubank(int banksize, int bankpos, int banknum) {
        for (int i = 0; i < banksize; ++i) {
            chr_map[i + bankpos] = (1024 * ((banksize * banknum) + i)) % chrsize;
        }
        //utils.printarray(chr_map);
    }
}