mirror of
https://github.com/ivanizag/izapple2.git
synced 2024-12-23 00:30:21 +00:00
196 lines
5.0 KiB
Go
196 lines
5.0 KiB
Go
package izapple2
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import (
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"fmt"
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"github.com/ivanizag/iz6502"
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)
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/*
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RomX from https://theromexchange.com/
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This complement uses the RomX API spec to switch main ROM and character generator ROM
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Only the font switch is implemented
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See:
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https://theromexchange.com/documentation/ROM%20X%20API%20Reference.pdf
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https://theromexchange.com/downloads/ROM%20X%2020-10-22.zip
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https://theromexchange.com/documentation/romxce/ROMXce%20API%20Reference.pdf
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For romX:
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It is not enough to intercept the ROM accesses. RomX intercept the 74LS138 in
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position F12, that has access to the full 0xc000-0xf000 on the Apple II+
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Firmware:
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- It first copies $D000-$DFFF to $6000 and runs there.
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go run *.go -rom ROMX.FIRM.dump -disk ROM\ X\ 20-10-22.dsk
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*/
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type romX struct {
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a *Apple2
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memory iz6502.Memory
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activationStep int
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systemBank uint8
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mainBank uint8
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tempBank uint8
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textBank uint8
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debug bool
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}
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var romXActivationSequence = []uint16{0xcaca, 0xcaca, 0xcafe}
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var romXceActivationSequence = []uint16{0xfaca, 0xfaca, 0xfafe}
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const (
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romxSetupBank = uint8(0)
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romXPlusSetSystemBankBaseAddress = uint16(0xcef0)
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romXPlusSetTextBankBaseAddress = uint16(0xcfd0)
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// Unknown
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//romXFirmwareMark0Address = uint16(0xdffe)
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//romXFirmwareMark0Value = uint8(0x4a)
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//romXFirmwareMark1Address = uint16(0xdfff)
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//romXFirmwareMark1Value = uint8(0xcd)
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romXceSelectTempBank = uint16(0xf850)
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romXceSelectMainBank = uint16(0xf851)
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romXceSetTempBank = uint16(0xf830) // 16 positions
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romXceSetMainBank = uint16(0xf800) // 16 positions
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romXcePresetTextBank = uint16(0xf810) // 16 positions
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romXceMCP7940SDC = uint16(0xf860) // 16 positions
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romXceLowerUpperBanks = uint16(0xf820) // 16 positions
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romXGetDefaultSystemBank = uint16(0xd034) // $00 to $0f
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romXGetDefaultTextBank = uint16(0xd02e) // $10 to $1f
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romXGetCurrentBootDelay = uint16(0xdeca) // $00 to $0f
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/*
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romXceEntryPointSetClock = uint16(0xc803)
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romXceEntryPointReadClock = uint16(0xc803)
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romXceEntryPointLauncherToRam = uint16(0xdfd9)
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romXceEntryPointLauncher = uint16(0xdfd0)
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*/
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)
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func newRomX(a *Apple2, memory iz6502.Memory) (*romX, error) {
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var rx romX
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rx.a = a
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rx.memory = memory
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rx.systemBank = 1
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rx.mainBank = 1
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rx.tempBank = 1
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rx.textBank = 0
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rx.debug = true
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if a.isApple2e {
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err := a.cg.load("<internal>/ROMXce Production 1Mb Text ROM V5.bin")
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if err != nil {
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return nil, err
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}
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}
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return &rx, nil
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}
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func (rx *romX) Peek(address uint16) uint8 {
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intercepted, value := rx.interceptAccess(address)
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if intercepted {
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return value
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}
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return rx.memory.Peek(address)
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}
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func (rx *romX) PeekCode(address uint16) uint8 {
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intercepted, value := rx.interceptAccess(address)
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if intercepted {
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return value
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}
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return rx.memory.PeekCode(address)
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}
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func (rx *romX) Poke(address uint16, value uint8) {
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rx.interceptAccess(address)
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rx.memory.Poke(address, value)
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}
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func (rx *romX) logf(format string, a ...interface{}) {
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msg := fmt.Sprintf(format, a...)
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fmt.Printf("[romX]%s\n", msg)
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}
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func (rx *romX) interceptAccess(address uint16) (bool, uint8) {
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// Intercept only $C080 to $FFFF as seen by the F12 chip
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if address < 0xc080 {
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return false, 0
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}
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// Setup mode when the setup bank is active
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if rx.systemBank == romxSetupBank {
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// Range commands
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nibble := uint8(address & 0xf)
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switch address & 0xfff0 {
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case romXceSetMainBank:
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rx.mainBank = nibble
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rx.logf("Main bank set to $%x", nibble)
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case romXcePresetTextBank:
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textBank := int(nibble)
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rx.a.cg.setPage(textBank)
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rx.logf("[romX]Text bank set to $%x", nibble)
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case romXceLowerUpperBanks:
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rx.logf("Configure lower upper banks $%x", address)
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case romXceSetTempBank:
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rx.tempBank = nibble
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rx.logf("Temp bank set to $%x", nibble)
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case romXceMCP7940SDC:
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rx.logf("Configure MCP7940 $%x", address)
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}
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// More commands
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switch address {
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case romXceSelectTempBank:
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rx.systemBank = rx.tempBank
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rx.logf("System bank set to temp bank $%x", rx.systemBank)
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case romXceSelectMainBank:
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rx.systemBank = rx.mainBank
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rx.logf("System bank set to main bank $%x", rx.systemBank)
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}
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// Queries
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switch address {
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case romXGetDefaultSystemBank:
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bank := rx.systemBank
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rx.logf("Peek in $%04x, current system bank %v", address, bank)
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return true, bank
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case romXGetDefaultTextBank:
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page := uint8(rx.a.cg.getPage() & 0xf)
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rx.logf("PeeK in $%04x, current text bank %v", address, page)
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return true, 0x10 + page
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case romXGetCurrentBootDelay:
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delay := uint8(5) // We don't care
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rx.logf("PeeK in $%04x, current boot delay %v", address, delay)
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return true, delay
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}
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return false, 0
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}
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// Activation sequence detection
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if address == romXceActivationSequence[rx.activationStep] {
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rx.activationStep++
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rx.logf("Activation step %v", rx.activationStep)
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if rx.activationStep == len(romXActivationSequence) {
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// Activation sequence completed
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rx.systemBank = romxSetupBank
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rx.activationStep = 0
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rx.logf("System bank set to 0, %v", rx.systemBank)
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}
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} else {
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rx.activationStep = 0
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}
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return false, 0
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}
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