izapple2/cardFastChip.go

package apple2

/*
Simulates just what is needed to make Total Replay use fast mode. Can change
from controlled speed to max speed the emulator can do.
Note: It ends up not being useful for Total Replay as loading from HD is already
very fast. HD blocks are loaded directly on the emulated RAM.

See:
	https://github.com/a2-4am/4cade/blob/master/src/hw.accel.a
	http://www.a2heaven.com/webshop/resources/pdf_document/18/82/c.pdf

*/

type cardFastChip struct {
	cardBase
	unlocked       bool
	unlockCounter  uint8
	enabled        bool
	accelerated    bool
	configRegister uint8
}

func buildFastChipRom() []uint8 {
	data := make([]uint8, 256)
	return data
}

const (
	fastChipUnlockToken   = 0x6a
	fastChipUnlockRepeats = 4
	fastChipNormalSpeed   = uint8(9)
)

func (c *cardFastChip) assign(a *Apple2, slot int) {
	// The softswitches are outside the card reserved ss
	// Only writes are implemented to avoid conflicts with the joysticks
	a.io.addSoftSwitchW(0x6a, func(_ *ioC0Page, value uint8) {
		if value == fastChipUnlockToken {
			c.unlockCounter++
			if c.unlockCounter >= fastChipUnlockRepeats {
				c.unlocked = true
			}
		} else {
			c.unlockCounter = 0
			c.unlocked = false
			c.enabled = false
		}
	}, "FASTCHIP-LOCK")

	a.io.addSoftSwitchW(0x6b, func(_ *ioC0Page, _ uint8) {
		if c.unlocked {
			c.enabled = true
		}
	}, "FASTCHIP-ENABLE")

	a.io.addSoftSwitchW(0x6d, func(_ *ioC0Page, value uint8) {
		if c.enabled {
			c.setSpeed(a, value)
		}
	}, "FASTCHIP-SPEED")

	a.io.addSoftSwitchW(0x6e, func(_ *ioC0Page, value uint8) {
		if c.enabled {
			c.configRegister = value
		}
	}, "FASTCHIP-CONFIG")

	a.io.addSoftSwitchW(0x6f, func(_ *ioC0Page, value uint8) {
		if c.enabled && c.configRegister == 0 {
			c.setSpeed(a, value)
		}
	}, "FASTCHIP-CONFIG")

	c.cardBase.assign(a, slot)
}

func (c *cardFastChip) setSpeed(a *Apple2, value uint8) {
	newAccelerated := (value > fastChipNormalSpeed)
	if newAccelerated == c.accelerated {
		// No change requested
		return
	}
	if newAccelerated {
		a.requestFastMode()
	} else {
		a.releaseFastMode()
	}
	c.accelerated = newAccelerated
}