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Accepting that memory mapping on a IIe is more complicated than I anticiapted, introduces mapping for all pages.

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Also picks a name for the Unenhanced Apple IIe ROM.
This commit is contained in:
Thomas Harte 2018-07-28 13:02:49 -04:00
parent 894998b163
commit bc2afe69e1
2 changed files with 71 additions and 52 deletions
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120
Machines/AppleII/AppleII.cpp
View File

@ -139,12 +139,40 @@ template <bool is_iie> class ConcreteMachine:
return dynamic_cast<AppleII::DiskIICard *>(cards_[5].get());
}
// MARK: - Memory Map
struct MemoryBlock {
uint8_t *read_pointer = nullptr;
uint8_t *write_pointer = nullptr;
} memory_blocks_[4]; // The IO page isn't included.
MemoryBlock cx_rom_block_; // This is the IO page, for an IIe.
// MARK: - Memory Map.
/*
The Apple II's paging mechanisms are byzantine to say the least. Painful is
another appropriate adjective.
On a II and II+ there are five distinct zones of memory:
0000 to c000 : the main block of RAM
c000 to d000 : the IO area, including card ROMs
d000 to e000 : the low ROM area, which can alternatively contain either one of two 4kb blocks of RAM with a language card
e000 onward : the rest of ROM, also potentially replaced with RAM by a language card
On a IIe with auxiliary memory the following orthogonal changes also need to be factored in:
0000 to 0200 : can be paged independently of the rest of RAM, other than part of the language card area which pages with it
0400 to 0800 : the text screen, can be configured to write to auxiliary RAM
2000 to 4000 : the graphics screen, which can be configured to write to auxiliary RAM
c100 to d000 : can be used to page an additional 3.75kb of ROM, replacing the IO area
c300 to c400 : can contain the same 256-byte segment of the ROM as if the whole IO area were switched, but while leaving cards visible in the rest
If dealt with as individual blocks in the inner loop, that would therefore imply mapping
an address to one of 12 potential pageable zones. So I've gone reductive and surrendered
to paging every 6502 page of memory independently. It makes the paging events more expensive,
but hopefully is clear.
Those 12 block, for the record:
0000 to 0200; 0200 to 0400; 0400 to 0800; 0800 to 2000;
2000 to 4000; 4000 to c000; c000 to c100; c100 to c300;
c300 to c400; c400 to d000; d000 to e000; e000+
*/
uint8_t *read_pages_[256]; // each is a pointer to the 256-block of memory the CPU should read when accessing that page of memory
uint8_t *write_pages_[256]; // as per read_pages_, but this is where the CPU should write. If a pointer is nullptr, don't write.
// MARK: - The language card.
struct {
@ -156,20 +184,15 @@ template <bool is_iie> class ConcreteMachine:
bool has_language_card_ = true;
void set_language_card_paging() {
uint8_t *const ram = alternative_zero_page_ ? aux_ram_ : ram_;
uint8_t *const rom = is_iie ? &rom_[3840] : rom_.data();
if(has_language_card_ && !language_card_.write) {
memory_blocks_[2].write_pointer = &ram[48*1024 + (language_card_.bank1 ? 0x1000 : 0x0000)];
memory_blocks_[3].write_pointer = &ram[56*1024];
} else {
memory_blocks_[2].write_pointer = memory_blocks_[3].write_pointer = nullptr;
}
printf("Configuring for %c%c%c [%c]\n", language_card_.read ? 'r' : '-', language_card_.write ? 'w' : '-', language_card_.bank1 ? '1' : '-', has_language_card_ ? 'c' : '-');
if(has_language_card_ && language_card_.read) {
memory_blocks_[2].read_pointer = &ram[48*1024 + (language_card_.bank1 ? 0x1000 : 0x0000)];
memory_blocks_[3].read_pointer = &ram[56*1024];
} else {
memory_blocks_[2].read_pointer = rom_.data() + (is_iie ? 3840 : 0);
memory_blocks_[3].read_pointer = memory_blocks_[2].read_pointer + 0x1000;
for(int target = 0xd0; target < 0x100; ++target) {
uint8_t *const ram_page = &ram[(target << 8) - ((target < 0xe0 && language_card_.bank1) ? 0x1000 : 0x0000)];
uint8_t *const rom_page = &rom[(target << 8) - 0xd000];
write_pages_[target] = has_language_card_ && !language_card_.write ? ram_page : nullptr;
read_pages_[target] = has_language_card_ && language_card_.read ? ram_page : rom_page;
}
}
@ -281,7 +304,7 @@ template <bool is_iie> class ConcreteMachine:
break;
case Target::Model::IIe:
rom_size += 3840;
rom_names.push_back("apple2e.rom");
rom_names.push_back("apple2eu.rom");
break;
}
const auto roms = rom_fetcher("AppleII", rom_names);
@ -303,12 +326,16 @@ template <bool is_iie> class ConcreteMachine:
}
// Set up the block that will provide CX ROM access on a IIe.
cx_rom_block_.read_pointer = rom_.data();
// cx_rom_block_.read_pointer = rom_.data();
// Set up the default memory blocks. On a II or II+ these values will never change.
// On a IIe they'll be affected by selection of auxiliary RAM.
memory_blocks_[0].read_pointer = memory_blocks_[0].write_pointer = ram_;
memory_blocks_[1].read_pointer = memory_blocks_[1].write_pointer = &ram_[0x200];
for(int c = 0; c < 0xc0; ++c) {
read_pages_[c] = write_pages_[c] = &ram_[c << 8];
}
for(int c = 0xc0; c < 0xd0; ++c) {
read_pages_[c] = write_pages_[c] = nullptr;
}
// Set proper values for the language card/ROM area.
set_language_card_paging();
@ -355,31 +382,14 @@ template <bool is_iie> class ConcreteMachine:
++ stretched_cycles_since_card_update_;
}
/*
There are five distinct zones of memory on an Apple II:
0000 to 0200 : the zero and stack pages, which can be paged independently on a IIe
0200 to c000 : the main block of RAM, which can be paged on a IIe
c000 to d000 : the IO area, including card ROMs
d000 to e000 : the low ROM area, which can contain indepdently-paged RAM with a language card
e000 onward : the rest of ROM, also potentially replaced with RAM by a language card
*/
uint16_t accessed_address = address;
MemoryBlock *block = nullptr;
if(address < 0x200) block = &memory_blocks_[0];
else if(address < 0xc000) {
if(address < 0x6000 && !isReadOperation(operation)) update_video();
block = &memory_blocks_[1];
accessed_address -= 0x200;
}
else if(address < 0xd000) {block = (internal_CX_rom_ && address >= 0xc100) ? &cx_rom_block_: nullptr; accessed_address -= 0xc100; }
else if(address < 0xe000) {block = &memory_blocks_[2]; accessed_address -= 0xd000; }
else { block = &memory_blocks_[3]; accessed_address -= 0xe000; }
bool has_updated_cards = false;
if(block) {
if(isReadOperation(operation)) *value = block->read_pointer[accessed_address];
else if(block->write_pointer) block->write_pointer[accessed_address] = *value;
if(read_pages_[address >> 8]) {
if(isReadOperation(operation)) *value = read_pages_[address >> 8][address & 0xff];
else if(write_pages_[address >> 8]) write_pages_[address >> 8][address & 0xff] = *value;
// if(!isReadOperation(operation) && address >= 0xd000) {
// printf("%02x -> %04x (%04x)\n", *value, address, &write_pages_[address >> 8][address & 0xff] - ram_);
// }
if(should_load_quickly_) {
// Check for a prima facie entry into RWTS.
@ -483,7 +493,7 @@ template <bool is_iie> class ConcreteMachine:
// Read-only switches.
switch(address) {
default:
printf("Unknown read from %04x\n", address);
// printf("Unknown read from %04x\n", address);
break;
case 0xc000:
@ -537,10 +547,10 @@ template <bool is_iie> class ConcreteMachine:
} else {
// Write-only switches. All IIe as currently implemented.
if(is_iie) {
printf("w %04x\n", address);
// printf("w %04x\n", address);
switch(address) {
default:
printf("Unknown write to %04x\n", address);
// printf("Unknown write to %04x\n", address);
break;
case 0xc006:
@ -565,7 +575,14 @@ template <bool is_iie> class ConcreteMachine:
// The alternative zero page setting affects both bank 0 and any RAM
// that's paged as though it were on a language card.
alternative_zero_page_ = !!(address&1);
memory_blocks_[0].read_pointer = memory_blocks_[0].write_pointer = alternative_zero_page_ ? aux_ram_ : ram_;
if(alternative_zero_page_) {
read_pages_[0] = aux_ram_;
} else {
read_pages_[0] = ram_;
}
read_pages_[1] = read_pages_[0] + 256;
write_pages_[0] = read_pages_[0];
write_pages_[1] = read_pages_[1];
set_language_card_paging();
break;
}
@ -638,6 +655,7 @@ template <bool is_iie> class ConcreteMachine:
// "The PRE-WRITE flip-flop is set by an odd read access in the $C08X range. It is reset by an even access or a write access."
language_card_.pre_write = isReadOperation(operation) ? (address&1) : false;
// Apply whatever the net effect of all that is to the memory map.
set_language_card_paging();
break;
}
@ -646,7 +664,7 @@ template <bool is_iie> class ConcreteMachine:
Communication with cards follows.
*/
if(!block && address >= 0xc090 && address < 0xc800) {
if(!read_pages_[address >> 8] && address >= 0xc090 && address < 0xc800) {
// If this is a card access, figure out which card is at play before determining
// the totality of who needs messaging.
int card_number = 0;

3
ROMImages/AppleII/readme.txt
View File

@ -4,7 +4,8 @@ Expected files:
apple2o.rom — an image at least 12kb big, in which the final 12kb is the original Apple II's ROM.
apple2.rom — an image at least 12kb big, in which the final 12kb is the Apple II+'s ROM.
apple2e.rom — a file at least 15.75kb big, in which the final 12kb is the main portion of the ROM, that is visible from $D000, and the 3.75kb before that is the portion that can be paged in from $C100.
apple2e.rom — a file at least 15.75kb big, in which the final 12kb is the main portion of the Enhanced IIe ROM, that is visible from $D000, and the 3.75kb before that is the portion that can be paged in from $C100.
apple2eu.rom — as per apple2e.rom, but for the Unenhanced Apple II.
apple2-character.rom — a 2kb image of the Apple IIe's character ROM.