izapple2/base64a.go

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package apple2
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import (
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"fmt"
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"github.com/ivanizag/apple2/core6502"
)
/*
Copam BASE64A adaptation.
*/
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// newBase64a instantiates an apple2
func newBase64a() *Apple2 {
var a Apple2
a.Name = "Base 64A"
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a.mmu = newMemoryManager(&a)
a.cpu = core6502.NewNMOS6502(a.mmu)
a.io = newIoC0Page(&a)
addApple2SoftSwitches(a.io)
addBase64aSoftSwitches(a.io)
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return &a
}
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const (
// There are 6 ROM chips. Each can have 4Kb or 8Kb. They can fill
// 2 or 4 banks with 2kb windows.
base64aRomBankSize = 12 * 1024
base64aRomBankCount = 4
base64aRomWindowSize = 2 * 1024
base64aRomChipCount = 6
)
func loadBase64aRom(a *Apple2) error {
// Load the 6 PROM dumps
romBanksBytes := make([][]uint8, base64aRomBankCount)
for j := range romBanksBytes {
romBanksBytes[j] = make([]uint8, 0, base64aRomBankSize)
}
for i := 0; i < base64aRomChipCount; i++ {
filename := fmt.Sprintf("<internal>/BASE64A_%X.BIN", 0xd0+i*0x08)
data, err := loadResource(filename)
if err != nil {
return err
}
for j := range romBanksBytes {
start := (j * base64aRomWindowSize) % len(data)
romBanksBytes[j] = append(romBanksBytes[j], data[start:start+base64aRomWindowSize]...)
}
}
// Create banks
for j := range romBanksBytes {
a.mmu.physicalROM[j] = newMemoryRange(0xd000, romBanksBytes[j])
}
// Start with first bank active
a.mmu.setActiveROMPage(0)
return nil
}
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func addBase64aSoftSwitches(io *ioC0Page) {
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// Other softswitches, not implemented but called from the ROM
io.addSoftSwitchW(0x0C, notImplementedSoftSwitchW, "80COLOFF")
io.addSoftSwitchW(0x0E, notImplementedSoftSwitchW, "ALTCHARSETOFF")
// Write on the speaker. That is a double access and should do nothing
// but works somehow on the BASE64A
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io.addSoftSwitchW(0x30, func(io *ioC0Page, value uint8) {
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speakerSoftSwitch(io)
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}, "SPEAKER")
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// ROM pagination softswitches. They use the annunciator 0 and 1
mmu := io.apple2.mmu
io.addSoftSwitchRW(0x58, func(*ioC0Page) uint8 {
p := mmu.getActiveROMPage()
mmu.setActiveROMPage(p & 2)
return 0
}, "ANN0OFF-ROM")
io.addSoftSwitchRW(0x59, func(*ioC0Page) uint8 {
p := mmu.getActiveROMPage()
mmu.setActiveROMPage(p | 1)
return 0
}, "ANN0ON-ROM")
io.addSoftSwitchRW(0x5A, func(*ioC0Page) uint8 {
p := mmu.getActiveROMPage()
mmu.setActiveROMPage(p & 1)
return 0
}, "ANN1OFF-ROM")
io.addSoftSwitchRW(0x5B, func(*ioC0Page) uint8 {
p := mmu.getActiveROMPage()
mmu.setActiveROMPage(p | 2)
return 0
}, "ANN1ON-ROM")
}
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func charGenColumnsMapBase64a(column int) int {
bit := column + 2
// Weird positions
if column == 6 {
bit = 2
} else if column == 0 {
bit = 1
}
return bit
}