mirror of
https://github.com/ivanizag/izapple2.git
synced 2024-12-22 09:30:19 +00:00
101 lines
3.0 KiB
Go
101 lines
3.0 KiB
Go
package apple2
|
|
|
|
/*
|
|
Apple II Memory Expansion Card
|
|
|
|
|
|
See:
|
|
http://www.apple-iigs.info/doc/fichiers/a2me.pdf
|
|
http://ae.applearchives.com/files/RamFactor_Manual_1.5.pdf
|
|
http://www.1000bit.it/support/manuali/apple/technotes/memx/tn.memx.1.html
|
|
|
|
There is a self test in ROM, address Cs0A.
|
|
|
|
From the RamFactor docs:
|
|
The RamFactor card has five addressable registers, which are addressed
|
|
according to the slot number the card is in:
|
|
$C080+slot * 16low byte of RAM address
|
|
$C081+slot * 16middle byte of RAM address
|
|
$C082+slot * 16high byte of RAM address
|
|
$C083+slot * 16data at addressed location
|
|
$C08F+slot * 16Firmware Bank Select
|
|
After power up or Control-Reset, the registers on the card are all in a
|
|
disabled state. They will be enabled by addressing any address in the firmware
|
|
page $Cs00-CsFF.
|
|
The three address bytes can be both written into and read from. If the card
|
|
has one Megabyte or less, reading the high address byte will always return a
|
|
value in the range $F0-FF. The top nybble can be any value when you write it,
|
|
but it will always be “F” when you read it. If the card has more than one
|
|
Megabyte of RAM, the top nybble will be a meaningful part of the address.
|
|
|
|
*/
|
|
const (
|
|
memoryExpansionSize256 = 256 * 1024
|
|
memoryExpansionSize512 = 512 * 1024
|
|
memoryExpansionSize768 = 768 * 1024
|
|
memoryExpansionSize1024 = 1024 * 1024
|
|
memoryExpansionMask = 0x000fffff // 10 bits, 1MB
|
|
)
|
|
|
|
type cardMemoryExpansion struct {
|
|
ram [memoryExpansionSize1024]uint8
|
|
index int
|
|
cardBase
|
|
}
|
|
|
|
func (c *cardMemoryExpansion) assign(a *Apple2, slot int) {
|
|
|
|
// Read pointer position
|
|
c.addCardSoftSwitchR(0, func(*ioC0Page) uint8 {
|
|
return uint8(c.index)
|
|
}, "MEMORYEXLOR")
|
|
c.addCardSoftSwitchR(1, func(*ioC0Page) uint8 {
|
|
return uint8(c.index >> 8)
|
|
}, "MEMORYEXMIR")
|
|
c.addCardSoftSwitchR(2, func(*ioC0Page) uint8 {
|
|
// Top nibble returned is 0xf
|
|
return uint8(c.index>>16) | 0xf0
|
|
}, "MEMORYEXHIR")
|
|
|
|
// Set pointer position
|
|
c.addCardSoftSwitchW(0, func(_ *ioC0Page, value uint8) {
|
|
c.index = (c.index &^ 0xff) + int(value)
|
|
}, "MEMORYEXLOW")
|
|
c.addCardSoftSwitchW(1, func(_ *ioC0Page, value uint8) {
|
|
c.index = (c.index &^ 0xff00) + int(value)<<8
|
|
}, "MEMORYEXMIW")
|
|
c.addCardSoftSwitchW(2, func(_ *ioC0Page, value uint8) {
|
|
// Only lo nibble is used
|
|
c.index = (c.index &^ 0xff0000) + int(value&0x0f)<<16
|
|
}, "MEMORYEXHIW")
|
|
|
|
// Read data
|
|
c.addCardSoftSwitchR(3, func(*ioC0Page) uint8 {
|
|
var value uint8
|
|
if c.index < len(c.ram) {
|
|
value = c.ram[c.index]
|
|
} else {
|
|
value = 0xde // Ram socket not populated
|
|
}
|
|
c.index = (c.index + 1) & memoryExpansionMask
|
|
return value
|
|
}, "MEMORYEXR")
|
|
|
|
// Write data
|
|
c.addCardSoftSwitchW(3, func(_ *ioC0Page, value uint8) {
|
|
if c.index < len(c.ram) {
|
|
c.ram[c.index] = value
|
|
}
|
|
c.index = (c.index + 1) & memoryExpansionMask
|
|
}, "MEMORYEXW")
|
|
|
|
// The rest of the softswitches return 255, at least on //e and //c
|
|
for i := uint8(4); i < 16; i++ {
|
|
c.addCardSoftSwitchR(i, func(*ioC0Page) uint8 {
|
|
return 255
|
|
}, "MEMORYEXUNUSEDR")
|
|
}
|
|
|
|
c.cardBase.assign(a, slot)
|
|
}
|