VRC2Mapper.java

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

import com.grapeshot.halfnes.*;

public class VRC2Mapper extends Mapper {
    //vrc2a mapper(INES #22); vrc2b is mapped to 23 along with the one form of vrc4

    int prgbank0, prgbank1 = 0;
    int[] chrbank = {0, 0, 0, 0, 0, 0, 0, 0};

    @Override
    public void loadrom() throws BadMapperException {
        // needs to be in every mapper. Fill with initial cfg
        super.loadrom();
        for (int i = 1; i <= 32; ++i) {
            //map last banks in to start off
            prg_map[32 - i] = prgsize - (1024 * i);
        }
        for (int i = 0; i < 8; ++i) {
            chr_map[i] = (1024 * i) & (chrsize - 1);
        }
    }

    @Override
    public final void cartWrite(int addr, int data) {
        if (addr < 0x8000 || addr > 0xffff) {
            super.cartWrite(addr, data);
            return;
        }
        boolean bit0 = ((addr & (utils.BIT1)) != 0);
        boolean bit1 = ((addr & (utils.BIT0)) != 0);
        switch (addr >> 12) {
            case 0x8:
                prgbank0 = data & 0xf;
                break;
            case 0x9:
                //mirroring
                switch (data & 1) {
                    case 0:
                        setmirroring(Mapper.MirrorType.V_MIRROR);
                        break;
                    case 1:
                        setmirroring(Mapper.MirrorType.H_MIRROR);
                        break; 
                }
                //4-4-2016: seems VRC2 only has 1 mirroring bit
                break;
            case 0xa:
                prgbank1 = data & 0xf;
                break;
            case 0xb:
            case 0xc:
            case 0xd:
            case 0xe:
                //chr bank select. black magic
                data &= 0xf;
                int whichreg = ((addr - 0xb000) >> 11) + ((bit1) ? 1 : 0);
                int oldval = chrbank[whichreg];
                if (!bit0) {
                    oldval &= 0xf0;
                    oldval |= data;
                } else {
                    oldval &= 0xf;
                    oldval |= (data << 4);
                }
                chrbank[whichreg] = oldval;
                break;
        }

        if (addr < 0xf000) {
            setbanks();
        }
    }

    private void setbanks() {
        //map prg banks
        //last 2 banks fixed to last two in rom
        for (int i = 1; i <= 16; ++i) {
            prg_map[32 - i] = prgsize - (1024 * i);
        }
        //first bank set to prg0 register
        for (int i = 0; i < 8; ++i) {
            prg_map[i] = (1024 * (i + 8 * prgbank0)) % prgsize;
        }
        //second bank set to prg1 register
        for (int i = 0; i < 8; ++i) {
            prg_map[i + 8] = (1024 * (i + 8 * prgbank1)) % prgsize;
        }

        //map chr banks
        for (int i = 0; i < 8; ++i) {
            setppubank(1, i, chrbank[i] >> 1);
        }

    }

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