izapple2/softSwitches2e.go

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package izapple2
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/*
See:
https://www.apple.asimov.net/documentation/hardware/machines/APPLE%20IIe%20Auxiliary%20Memory%20Softswitches.pdf
*/
const (
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ioFlagAltChar uint8 = 0x1E
ioFlag80Col uint8 = 0x1F
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)
const (
screenDrawCycles = uint64(12480 + 4550)
screenVertBlankingCycles = uint64(4550)
)
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func addApple2ESoftSwitches(io *ioC0Page) {
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// New MMU read softswithes
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mmu := io.apple2.mmu
addSoftSwitchesMmu(io, 0x02, 0x03, 0x13, &mmu.altMainRAMActiveRead, "RAMRD")
addSoftSwitchesMmu(io, 0x04, 0x05, 0x14, &mmu.altMainRAMActiveWrite, "RAMWRT")
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addSoftSwitchesMmu(io, 0x06, 0x07, 0x15, &mmu.intCxROMActive, "INTCXROM")
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addSoftSwitchesMmu(io, 0x08, 0x09, 0x16, &mmu.altZeroPage, "ALTZP")
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addSoftSwitchesMmu(io, 0x0a, 0x0b, 0x17, &mmu.slotC3ROMActive, "SLOTC3ROM")
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mmu.slotC3ROMActive = false // Default behavior in II+ was true
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addSoftSwitchesMmu(io, 0x00, 0x01, 0x18, &mmu.store80Active, "80STORE")
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// New IOU read softswithes
addSoftSwitchesIou(io, 0x0c, 0x0d, 0x1f, ioFlag80Col, "80COL")
addSoftSwitchesIou(io, 0x0e, 0x0f, 0x1e, ioFlagAltChar, "ALTCHARSET")
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// Previous read softswithes
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io.addSoftSwitchR(0x1A, getStatusSoftSwitch(io, ioFlagText), "TEXT")
io.addSoftSwitchR(0x1B, getStatusSoftSwitch(io, ioFlagMixed), "MIXED")
io.addSoftSwitchR(0x1C, getStatusSoftSwitch(io, ioFlagSecondPage), "PAGE2")
io.addSoftSwitchR(0x1D, getStatusSoftSwitch(io, ioFlagHiRes), "HIRES")
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io.addSoftSwitchR(0x11, func() uint8 {
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return ssFromBool(mmu.lcAltBank)
}, "BSRBANK2")
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io.addSoftSwitchR(0x12, func() uint8 {
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return ssFromBool(mmu.lcActiveRead)
}, "BSRREADRAM")
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io.addSoftSwitchR(0x19, func() uint8 {
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// See "Inside Apple IIe", page 268
// See http://rich12345.tripod.com/aiivideo/vbl.html
// For each screen draw:
// 12480 cycles drawing lines, VERTBLANK = $00
// 4550 cycles doing the return to position (0,0), VERTBLANK = $80
// Vert blank takes 12480 cycles every page redraw
cycles := io.apple2.cpu.GetCycles() % screenDrawCycles
if cycles <= screenVertBlankingCycles {
return ssOn
}
return ssOff
}, "VERTBLANK")
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//io.softSwitchesData[ioFlagAltChar] = ssOn // Not sure about this.
}
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func addSoftSwitchesMmu(io *ioC0Page, addressClear uint8, addressSet uint8, AddressGet uint8, flag *bool, name string) {
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io.addSoftSwitchW(addressClear, func(uint8) {
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*flag = false
}, name+"OFF")
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io.addSoftSwitchW(addressSet, func(uint8) {
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*flag = true
}, name+"ON")
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io.addSoftSwitchR(AddressGet, func() uint8 {
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return ssFromBool(*flag)
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}, name)
}
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func addSoftSwitchesIou(io *ioC0Page, addressClear uint8, addressSet uint8, AddressGet uint8, ioFlag uint8, name string) {
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io.addSoftSwitchW(addressClear, func(uint8) {
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io.softSwitchesData[ioFlag] = ssOff
}, name+"OFF")
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io.addSoftSwitchW(addressSet, func(uint8) {
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io.softSwitchesData[ioFlag] = ssOn
}, name+"ON")
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io.addSoftSwitchR(AddressGet, func() uint8 {
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return io.softSwitchesData[ioFlag]
}, name)
}