/
mmc2.go
311 lines (267 loc) · 6.52 KB
/
mmc2.go
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package nes
import (
"fmt"
"../rp2ago3"
"../rp2cgo2"
)
type MMC2Registers struct {
PRGBank uint8
CHRBank0 uint8
CHRBank1 uint8
CHRBank2 uint8
CHRBank3 uint8
Mirroring uint8
Latch0 uint8
Latch1 uint8
}
type MMC2 struct {
*ROMFile
Registers MMC2Registers
}
func (reg *MMC2Registers) Reset() {
reg.PRGBank = 0x00
reg.CHRBank0 = 0x00
reg.CHRBank1 = 0x00
reg.CHRBank2 = 0x00
reg.CHRBank3 = 0x00
reg.Mirroring = 0x00
reg.Latch0 = 0xfd
reg.Latch1 = 0xfe
}
func NewMMC2(romf *ROMFile) *MMC2 {
mmc2 := &MMC2{
ROMFile: romf,
}
// divide 8KB CHR banks into 4KB banks since we may be
// swapping 4KB banks
if romf.CHRBanks > 0 {
vromBanks := make([][]uint8, uint16(romf.CHRBanks)*2)
for n := 0; n < int(romf.CHRBanks); n++ {
vromBanks[2*n] = romf.VROMBanks[n][0x0000:0x1000]
vromBanks[(2*n)+1] = romf.VROMBanks[n][0x1000:0x2000]
}
romf.VROMBanks = vromBanks
romf.CHRBanks *= 2
}
// divide 16KB PRG banks into 8KB banks since we may be
// swapping 8KB banks
if romf.PRGBanks > 0 {
romBanks := make([][]uint8, uint16(romf.PRGBanks)*2)
for n := 0; n < int(romf.PRGBanks); n++ {
romBanks[2*n] = romf.ROMBanks[n][0x0000:0x2000]
romBanks[(2*n)+1] = romf.ROMBanks[n][0x2000:0x4000]
}
romf.ROMBanks = romBanks
romf.PRGBanks *= 2
}
mmc2.Registers.Reset()
mmc2.setTables(mmc2.Tables())
return mmc2
}
func (mmc2 *MMC2) String() string {
return mmc2.ROMFile.String() +
fmt.Sprintf("Mapper: 9 (MMC2)")
}
func (mmc2 *MMC2) Mappings(which rp2ago3.Mapping) (fetch, store []uint16) {
fetch = []uint16{}
store = []uint16{}
switch which {
case rp2ago3.PPU:
if mmc2.CHRBanks > 0 {
// CHR bank 1
for i := uint32(0x0000); i <= 0x0fff; i++ {
fetch = append(fetch, uint16(i))
store = append(store, uint16(i))
}
// CHR bank 2
for i := uint32(0x1000); i <= 0x1fff; i++ {
fetch = append(fetch, uint16(i))
store = append(store, uint16(i))
}
}
case rp2ago3.CPU:
if mmc2.PRGBanks > 0 {
// PRG bank 1
for i := uint32(0x8000); i <= 0x9fff; i++ {
store = append(store, uint16(i))
fetch = append(fetch, uint16(i))
}
// PRG bank 2
for i := uint32(0xa000); i <= 0xbfff; i++ {
store = append(store, uint16(i))
fetch = append(fetch, uint16(i))
}
// PRG bank 3
for i := uint32(0xc000); i <= 0xdfff; i++ {
store = append(store, uint16(i))
fetch = append(fetch, uint16(i))
}
// PRG bank 4
for i := uint32(0xe000); i <= 0xffff; i++ {
store = append(store, uint16(i))
fetch = append(fetch, uint16(i))
}
}
}
return
}
func (mmc2 *MMC2) Reset() {
mmc2.Registers.Reset()
}
func (mmc2 *MMC2) Fetch(address uint16) (value uint8) {
switch {
// PPU only
// CHR banks 1 & 2
case address >= 0x0000 && address <= 0x1fff:
index := address & 0x0fff
lower, upper := mmc2.chrBanks()
switch {
// CHR bank 1
case address >= 0x0000 && address <= 0x0fff:
if mmc2.CHRBanks > 0 {
value = mmc2.VROMBanks[lower][index]
}
// CHR bank 2
case address >= 0x1000 && address <= 0x1fff:
if mmc2.CHRBanks > 0 {
value = mmc2.VROMBanks[upper][index]
}
}
switch {
case address == 0x0fd8:
mmc2.Registers.Latch0 = 0xfd
case address == 0x0fe8:
mmc2.Registers.Latch0 = 0xfe
case address >= 0x1fd8 && address <= 0x1fdf:
mmc2.Registers.Latch1 = 0xfd
case address >= 0x1fe8 && address <= 0x1fef:
mmc2.Registers.Latch1 = 0xfe
}
// CPU only
case address >= 0x8000 && address <= 0xffff:
index := address & 0x1fff
switch {
// PRG bank 1
case address >= 0x8000 && address <= 0x9fff:
if mmc2.PRGBanks > 0 {
bank := mmc2.prgBank()
value = mmc2.ROMBanks[bank][index]
}
// PRG bank 2
case address >= 0xa000 && address <= 0xbfff:
if mmc2.PRGBanks > 0 {
value = mmc2.ROMBanks[mmc2.PRGBanks-3][index]
}
// PRG bank 3
case address >= 0xc000 && address <= 0xdfff:
if mmc2.PRGBanks > 0 {
value = mmc2.ROMBanks[mmc2.PRGBanks-2][index]
}
// PRG bank 4
case address >= 0xe000 && address <= 0xffff:
if mmc2.PRGBanks > 0 {
value = mmc2.ROMBanks[mmc2.PRGBanks-1][index]
}
}
}
return
}
func (mmc2 *MMC2) Store(address uint16, value uint8) (oldValue uint8) {
switch {
// PPU only
// CHR banks 1 & 2
case address >= 0x0000 && address <= 0x1fff:
index := address & 0x0fff
lower, upper := mmc2.chrBanks()
switch {
// CHR bank 1
case address >= 0x0000 && address <= 0x0fff:
if mmc2.CHRBanks > 0 {
mmc2.VROMBanks[lower][index] = value
}
// CHR bank 2
case address >= 0x1000 && address <= 0x1fff:
if mmc2.CHRBanks > 0 {
mmc2.VROMBanks[upper][index] = value
}
}
// CPU only
// PRG banks 1 & 2
case address >= 0x8000 && address <= 0x9fff:
bank := mmc2.prgBank()
index := address & 0x1fff
if mmc2.PRGBanks > 0 {
mmc2.ROMBanks[bank][index] = value
}
// PRG bank select
case address >= 0xa000 && address <= 0xafff:
mmc2.Registers.PRGBank = value
// CHR $fd/0000 bank select
case address >= 0xb000 && address <= 0xbfff:
mmc2.Registers.CHRBank0 = value
// CHR $fe/0000 bank select
case address >= 0xc000 && address <= 0xcfff:
mmc2.Registers.CHRBank1 = value
// CHR $fd/1000 bank select
case address >= 0xd000 && address <= 0xdfff:
mmc2.Registers.CHRBank2 = value
// CHR $fe/1000 bank select
case address >= 0xe000 && address <= 0xefff:
mmc2.Registers.CHRBank3 = value
// Mirroring
case address >= 0xf000 && address <= 0xffff:
oldMirroring := mmc2.mirroring()
mmc2.Registers.Mirroring = value
if mmc2.mirroring() != oldMirroring {
mmc2.setTables(mmc2.Tables())
}
}
return
}
func (mmc2 *MMC2) prgBank() uint8 {
return mmc2.Registers.PRGBank & 0x0f
}
func (mmc2 *MMC2) chrBank0() (bank uint8) {
return mmc2.Registers.CHRBank0 & 0x1f
}
func (mmc2 *MMC2) chrBank1() (bank uint8) {
return mmc2.Registers.CHRBank1 & 0x1f
}
func (mmc2 *MMC2) chrBank2() (bank uint8) {
return mmc2.Registers.CHRBank2 & 0x1f
}
func (mmc2 *MMC2) chrBank3() (bank uint8) {
return mmc2.Registers.CHRBank3 & 0x1f
}
func (mmc2 *MMC2) mirroring() rp2cgo2.Mirroring {
switch mmc2.Registers.Mirroring & 0x01 {
case 0:
return rp2cgo2.Vertical
default:
return rp2cgo2.Horizontal
}
}
func (mmc2 *MMC2) chrBanks() (lower, upper uint8) {
switch mmc2.Registers.Latch0 {
case 0xfd:
lower = mmc2.chrBank0()
case 0xfe:
lower = mmc2.chrBank1()
}
switch mmc2.Registers.Latch1 {
case 0xfd:
upper = mmc2.chrBank2()
case 0xfe:
upper = mmc2.chrBank3()
}
return
}
func (mmc2 *MMC2) Tables() (t0, t1, t2, t3 int) {
switch mmc2.mirroring() {
case rp2cgo2.Vertical:
t0, t1, t2, t3 = 0, 1, 0, 1
case rp2cgo2.Horizontal:
t0, t1, t2, t3 = 0, 0, 1, 1
}
return
}