izapple2/cardSaturn.go

226 lines
4.4 KiB
Go

package apple2
import (
"encoding/binary"
"io"
)
/*
RAM card with 128Kb. It's like 8 language cards.
http://www.applelogic.org/files/SATURN128MAN.pdf
*/
type cardSaturn struct {
cardBase
readState bool
writeState int
activeBank int
activeBlock int
ramBankA [saturnBlocks]*memoryRange // First 4kb to map in 0xD000-0xDFFF
ramBankB [saturnBlocks]*memoryRange // Second 4kb to map in 0xD000-0xDFFF
ramUpper [saturnBlocks]*memoryRange // Upper 8kb to map in 0xE000-0xFFFF
}
const (
// Write enabling requires two sofstwitch accesses
saturnWriteDisabled = 0
saturnWriteHalfEnabled = 1
saturnWriteEnabled = 2
)
const (
saturnBlocks = 8
)
func (c *cardSaturn) assign(a *Apple2, slot int) {
c.readState = false
c.writeState = lcWriteEnabled
c.activeBank = 1
for i := 0; i < saturnBlocks; i++ {
c.ramBankA[i] = newMemoryRange(0xd000, make([]uint8, 0x1000))
c.ramBankB[i] = newMemoryRange(0xd000, make([]uint8, 0x1000))
c.ramUpper[i] = newMemoryRange(0xe000, make([]uint8, 0x2000))
}
for i := 0x0; i <= 0xf; i++ {
iCopy := i
c.ssr[iCopy] = func(*ioC0Page) uint8 {
c.ssAction(iCopy, false)
return 0
}
c.ssw[iCopy] = func(*ioC0Page, uint8) {
c.ssAction(iCopy, true)
}
}
c.cardBase.assign(a, slot)
c.applyState()
}
func (c *cardSaturn) ssAction(ss int, write bool) {
switch ss {
case 0:
// RAM read, no writes
c.activeBank = 0
c.readState = true
c.writeState = lcWriteDisabled
case 1:
// ROM read, RAM write
c.activeBank = 0
c.readState = false
c.writeState++
case 2:
// ROM read, no writes
c.activeBank = 0
c.readState = false
c.writeState = lcWriteDisabled
case 3:
//RAM read, RAM write
c.activeBank = 0
c.readState = true
c.writeState++
case 4:
c.activeBlock = 0
case 5:
c.activeBlock = 1
case 6:
c.activeBlock = 2
case 7:
c.activeBlock = 3
case 8:
// RAM read, no writes
c.activeBank = 1
c.readState = true
c.writeState = lcWriteDisabled
case 9:
// ROM read, RAM write
c.activeBank = 1
c.readState = false
c.writeState++
case 10:
// ROM read, no writes
c.activeBank = 1
c.readState = false
c.writeState = lcWriteDisabled
case 11:
//RAM read, RAM write
c.activeBank = 1
c.readState = true
c.writeState++
case 12:
c.activeBlock = 4
case 13:
c.activeBlock = 5
case 14:
c.activeBlock = 6
case 15:
c.activeBlock = 7
}
if c.writeState > lcWriteEnabled {
c.writeState = lcWriteEnabled
}
// Writing to the softswtich disables writes.
if write {
c.writeState = lcWriteDisabled
}
c.applyState()
}
func (c *cardSaturn) getActiveBank() [8]*memoryRange {
if c.activeBank == 0 {
return c.ramBankA
}
return c.ramBankB
}
func (c *cardSaturn) applyState() {
mmu := c.a.mmu
block := c.activeBlock
if c.readState {
mmu.setPagesRead(0xd0, 0xdf, c.getActiveBank()[block])
mmu.setPagesRead(0xe0, 0xff, c.ramUpper[block])
} else {
mmu.setPagesRead(0xd0, 0xff, mmu.physicalROM)
}
if c.writeState == lcWriteEnabled {
mmu.setPagesWrite(0xd0, 0xdf, c.getActiveBank()[block])
mmu.setPagesWrite(0xe0, 0xff, c.ramUpper[block])
} else {
mmu.setPagesWrite(0xd0, 0xff, nil)
}
}
func (c *cardSaturn) save(w io.Writer) error {
for i := 0; i < saturnBlocks; i++ {
err := binary.Write(w, binary.BigEndian, c.readState)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.writeState)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.activeBank)
if err != nil {
return err
}
err = binary.Write(w, binary.BigEndian, c.activeBlock)
if err != nil {
return err
}
err = c.ramBankA[i].save(w)
if err != nil {
return err
}
err = c.ramBankB[i].save(w)
if err != nil {
return err
}
err = c.ramUpper[i].save(w)
if err != nil {
return err
}
}
return c.cardBase.save(w)
}
func (c *cardSaturn) load(r io.Reader) error {
for i := 0; i < saturnBlocks; i++ {
err := binary.Read(r, binary.BigEndian, &c.readState)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.writeState)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.activeBank)
if err != nil {
return err
}
err = binary.Read(r, binary.BigEndian, &c.activeBlock)
if err != nil {
return err
}
err = c.ramBankA[i].load(r)
if err != nil {
return err
}
err = c.ramBankB[i].load(r)
if err != nil {
return err
}
err = c.ramUpper[i].load(r)
c.applyState()
}
return c.cardBase.load(r)
}