2024-03-04 21:36:45 +01:00

160 lines
4.0 KiB

package izapple2
import "fmt"
Brain board card for Apple II
The Brain Board card has 2 banks of ROM to replace the main ROM
A 27c256 ROM (32k) is used, with the following mapping:
0x0000-0x00ff: lower card rom maps to $Csxx
0x1000-0x37ff: lower bank rom maps to $D000 to $F7FF
0x3800-0x3fff: F8 lower bank rom maps to $F800 to $FFFF
0x4000-0x40ff: upper card rom maps to $Csxx
0x5000-0x77ff: upper bank rom maps to $D000 to $F7FF
0x7800-0x7fff: F8 upper bank rom maps to $F800 to $FFFF
DIP SWitches_
1-ON : The range F8 can be replaced
1-OFF: The range F8 is not replaced
3-ON ,4-OFF: The motherboard ROM can be used
3-OFF,4-ON : The motherboard ROM is always replaced
5-ON ,6-OFF: The lower bank is used and mapped to Bank A
5-OFF,6-ON : The lower bank is not used (A can be motherboards or uppers)
7-ON ,8-OFF: The upper bank is used and mapper to bank B
7-OFF,8-ON : The upper bank is not used (B can be motherboards or lowers)
Switches and softswitches:
Up, $COsO - SS clear: A bank selected
Down, $COs1 - SS set: B bank selected
// CardBrainBoard represents a Brain Board card
type CardBrainBoard struct {
isBankB bool
isMotherboardRomEnabled bool
dip1_replaceF8 bool
dip34_useMotherboardRom bool
dip56_lowerInA bool
dip78_upperInB bool
rom []uint8
func newCardBrainBoardBuilder() *cardBuilder {
return &cardBuilder{
name: "Brain Board",
description: "Firmware card. It has two ROM banks",
defaultParams: &[]paramSpec{
{"rom", "ROM file to load", "<internal>/wozaniam_integer.rom"},
{"dips", "DIP switches, leftmost is DIP 1", "1-011010"},
{"switch", "Bank selected at boot, 'up' or 'down'", "up"},
buildFunc: func(params map[string]string) (Card, error) {
var c CardBrainBoard
var err error
bank := paramsGetString(params, "switch")
if bank == "up" {
c.isBankB = false
} else if bank == "down" {
c.isBankB = true
} else {
return nil, fmt.Errorf("invalid bank '%s', must be up or down", bank)
dips, err := paramsGetDIPs(params, "dips", 8)
if err != nil {
return nil, err
c.dip1_replaceF8 = dips[1]
if dips[3] == dips[4] {
return nil, fmt.Errorf("DIP switches 3 and 4 must be different")
if dips[5] == dips[6] {
return nil, fmt.Errorf("DIP switches 5 and 6 must be different")
if dips[7] == dips[8] {
return nil, fmt.Errorf("DIP switches 7 and 8 must be different")
c.dip34_useMotherboardRom = dips[3]
c.dip56_lowerInA = dips[5]
c.dip78_upperInB = dips[7]
romFile := paramsGetPath(params, "rom")
data, _, err := LoadResource(romFile)
if err != nil {
return nil, err
if len(data) != 0x8000 {
return nil, fmt.Errorf("the ROM file for the Brainboard must be 32k")
c.isMotherboardRomEnabled = true
c.rom = data
c.romCxxx = &c
return &c, nil
func (c *CardBrainBoard) updateState() {
isMotherboardRomEnabled := c.dip34_useMotherboardRom &&
((!c.dip56_lowerInA && !c.isBankB) || (!c.dip78_upperInB && c.isBankB))
if isMotherboardRomEnabled && !c.isMotherboardRomEnabled {
} else if !isMotherboardRomEnabled && c.isMotherboardRomEnabled {
c.isMotherboardRomEnabled = isMotherboardRomEnabled
func (c *CardBrainBoard) assign(a *Apple2, slot int) {
c.addCardSoftSwitchRW(0, func() uint8 {
c.isBankB = false
return 0x55
c.addCardSoftSwitchRW(1, func() uint8 {
c.isBankB = true
return 0x55
c.cardBase.assign(a, slot)
func (c *CardBrainBoard) translateAddress(address uint16) uint16 {
if c.isBankB {
return address - 0xc000 + 0x4000
} else {
return address - 0xc000
func (c *CardBrainBoard) peek(address uint16) uint8 {
return c.rom[c.translateAddress(address)]
func (c *CardBrainBoard) poke(address uint16, value uint8) {
// Nothing