112 lines
2.6 KiB
Go
112 lines
2.6 KiB
Go
package apple2
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import "fmt"
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/*
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Copam BASE64A adaptation.
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*/
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// Base64a extends an Apple2
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type Base64a struct {
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a *Apple2
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romBanks [4]*memoryRange
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romBank uint8
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}
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// NewBase64a instantiates an apple2
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func NewBase64a(a *Apple2) *Base64a {
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var b Base64a
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b.a = a
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a.Name = "Base 64A"
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b.loadRom()
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// Configure the character generator
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if !a.cg.customRom {
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a.cg.load("<internal>/BASE64A_ROM7_CharGen.BIN")
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}
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a.cg.setColumnMap(base64aCharGenColumnsMap)
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a.cg.setPage(1)
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return &b
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}
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func base64aCharGenColumnsMap(column int) int {
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bit := column + 2
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// Weird positions
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if column == 6 {
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bit = 2
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} else if column == 0 {
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bit = 1
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}
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return bit
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}
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const (
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// There are 6 ROM chips. Each can have 4Kb or 8Kb. They can fill
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// 2 or 4 banks with 2kb windows.
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base64aRomBankSize = 12 * 1024
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base64aRomBankCount = 4
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base64aRomWindowSize = 2 * 1024
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base64aRomChipCount = 6
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)
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func (b *Base64a) loadRom() {
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// Load the 6 PROM dumps
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romBanksBytes := make([][]uint8, base64aRomBankCount)
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for j := range romBanksBytes {
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romBanksBytes[j] = make([]uint8, 0, base64aRomBankSize)
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}
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for i := 0; i < base64aRomChipCount; i++ {
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filename := fmt.Sprintf("<internal>/BASE64A_%X.BIN", 0xd0+i*0x08)
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data := loadResource(filename)
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for j := range romBanksBytes {
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start := (j * base64aRomWindowSize) % len(data)
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romBanksBytes[j] = append(romBanksBytes[j], data[start:start+base64aRomWindowSize]...)
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}
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}
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for j := range romBanksBytes {
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b.romBanks[j] = newMemoryRange(0xd000, romBanksBytes[j])
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}
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// Start with first bank active
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b.changeRomBank(0)
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// Add rom soft switches. They use the annunciator 0 and 1
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b.a.io.addSoftSwitchRW(0x58, func(*ioC0Page) uint8 {
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b.changeRomBank(b.romBank & 2)
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return 0
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})
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b.a.io.addSoftSwitchRW(0x59, func(*ioC0Page) uint8 {
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b.changeRomBank(b.romBank | 1)
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return 0
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})
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b.a.io.addSoftSwitchRW(0x5A, func(*ioC0Page) uint8 {
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b.changeRomBank(b.romBank & 1)
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return 0
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})
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b.a.io.addSoftSwitchRW(0x5B, func(*ioC0Page) uint8 {
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b.changeRomBank(b.romBank | 2)
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return 0
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})
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// Other softswitches
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b.a.io.addSoftSwitchW(0x0C, notImplementedSoftSwitchW) // 80 columns off?
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b.a.io.addSoftSwitchW(0x0E, notImplementedSoftSwitchW) // Alt char off?
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// Write on the speaker. That is a double access and should do nothing
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// but works somehow on the BASE64A
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b.a.io.addSoftSwitchW(0x30, func(io *ioC0Page, value uint8) {
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getSpeakerSoftSwitch(io)
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})
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}
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func (b *Base64a) changeRomBank(bank uint8) {
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b.romBank = bank
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//fmt.Printf("Change to ROM bank #%v\n", b.romBank)
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b.a.mmu.physicalROM = b.romBanks[b.romBank]
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b.a.mmu.resetRomPaging() // If rom was not active. This is going to far?
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}
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