mirror of
https://github.com/TomHarte/CLK.git
synced 2024-06-29 00:29:34 +00:00
538 lines
20 KiB
C++
538 lines
20 KiB
C++
//
|
||
// MemoryMap.hpp
|
||
// Clock Signal
|
||
//
|
||
// Created by Thomas Harte on 25/10/2020.
|
||
// Copyright © 2020 Thomas Harte. All rights reserved.
|
||
//
|
||
|
||
#ifndef Machines_Apple_AppleIIgs_MemoryMap_hpp
|
||
#define Machines_Apple_AppleIIgs_MemoryMap_hpp
|
||
|
||
#include <array>
|
||
#include <vector>
|
||
|
||
#include "../AppleII/LanguageCardSwitches.hpp"
|
||
#include "../AppleII/AuxiliaryMemorySwitches.hpp"
|
||
|
||
namespace Apple {
|
||
namespace IIgs {
|
||
|
||
class MemoryMap {
|
||
public:
|
||
// MARK: - Initial construction and configuration.
|
||
|
||
MemoryMap() : auxiliary_switches_(*this), language_card_(*this) {}
|
||
|
||
void set_storage(std::vector<uint8_t> &ram, std::vector<uint8_t> &rom) {
|
||
// Keep a pointer for later; also note the proper RAM offset.
|
||
ram_base = ram.data();
|
||
shadow_base[1] = &ram[ram.size() - 128*1024];
|
||
|
||
// Establish bank mapping.
|
||
uint8_t next_region = 0;
|
||
auto region = [&next_region, this]() -> uint8_t {
|
||
assert(next_region != regions.size());
|
||
return next_region++;
|
||
};
|
||
auto set_region = [this](uint8_t bank, uint16_t start, uint16_t end, uint8_t region) {
|
||
assert((end == 0xffff) || !(end&0xff));
|
||
assert(!(start&0xff));
|
||
|
||
// Fill in memory map.
|
||
size_t target = size_t((bank << 8) | (start >> 8));
|
||
for(int c = start; c < end; c += 0x100) {
|
||
region_map[target] = region;
|
||
++target;
|
||
}
|
||
};
|
||
auto set_regions = [this, set_region, region](uint8_t bank, std::initializer_list<uint16_t> addresses, std::vector<uint8_t> allocated_regions = {}) {
|
||
uint16_t previous = 0x0000;
|
||
auto next_region = allocated_regions.begin();
|
||
for(uint16_t address: addresses) {
|
||
set_region(bank, previous, address, next_region != allocated_regions.end() ? *next_region : region());
|
||
previous = address;
|
||
assert(next_region != allocated_regions.end() || allocated_regions.empty());
|
||
if(next_region != allocated_regions.end()) ++next_region;
|
||
}
|
||
assert(next_region == allocated_regions.end());
|
||
};
|
||
|
||
// Current beliefs about the IIgs memory map:
|
||
//
|
||
// * language card banking applies to banks $00, $01, $e0 and $e1;
|
||
// * auxiliary memory switches apply to banks $00 only;
|
||
// * shadowing may be enabled only on banks $00 and $01, or on all RAM pages.
|
||
//
|
||
// So banks $00 and $01 need their own divided spaces at the shadowing resolution,
|
||
// all the other fast RAM banks can share a set of divided spaces, $e0 and $e1 need
|
||
// to be able to deal with language card-level division but no further, and the pure
|
||
// ROM pages don't need to be subdivided at all.
|
||
|
||
// Reserve region 0 as that for unmapped memory.
|
||
region();
|
||
|
||
// Bank $00: all locations potentially affected by the auxiliary switches or the
|
||
// language switches. Which will naturally align with shadowable zones.
|
||
set_regions(0x00, {
|
||
0x0200, 0x0400, 0x0800, 0x0c00,
|
||
0x2000, 0x4000, 0x6000,
|
||
0xc000, 0xc100, 0xc300, 0xc400, 0xc800,
|
||
0xd000, 0xe000,
|
||
0xffff
|
||
});
|
||
|
||
// Bank $01: all locations potentially affected by the language switches, by shadowing,
|
||
// or marked for IO.
|
||
set_regions(0x01, {
|
||
0x0400, 0x0800, 0x0c00,
|
||
0x2000, 0x4000, 0x6000, 0xa000,
|
||
0xc000, 0xc100, 0xc300, 0xc400, 0xc800,
|
||
0xd000, 0xe000,
|
||
0xffff
|
||
});
|
||
|
||
// Banks $02–[end of RAM]: all locations potentially affected by shadowing.
|
||
const uint8_t fast_ram_bank_count = uint8_t((ram.size() - 128*1024) / 65536);
|
||
if(fast_ram_bank_count > 2) {
|
||
const std::vector<uint8_t> evens = {
|
||
region(), // 0x0000 – 0x0400.
|
||
region(), // 0x0400 – 0x0800.
|
||
region(), // 0x0800 – 0x0c00.
|
||
region(), // 0x0c00 – 0x2000.
|
||
region(), // 0x2000 – 0x4000.
|
||
region(), // 0x4000 – 0x6000.
|
||
region(), // 0x6000 – [end].
|
||
};
|
||
const std::vector<uint8_t> odds = {
|
||
region(), // 0x0000 – 0x0400.
|
||
region(), // 0x0400 – 0x0800.
|
||
region(), // 0x0800 – 0x0c00.
|
||
region(), // 0x0c00 – 0x2000.
|
||
region(), // 0x2000 – 0x4000.
|
||
region(), // 0x4000 – 0x6000.
|
||
region(), // 0x6000 – 0xa000.
|
||
region(), // 0xa000 – [end].
|
||
};
|
||
for(uint8_t bank = 0x02; bank < fast_ram_bank_count; bank += 2) {
|
||
set_regions(bank, {0x0400, 0x0800, 0x0c00, 0x2000, 0x4000, 0x6000, 0xffff}, evens);
|
||
set_regions(bank+1, {0x0400, 0x0800, 0x0c00, 0x2000, 0x4000, 0x6000, 0xa000, 0xffff}, odds);
|
||
}
|
||
}
|
||
|
||
// [Banks $80–$e0: empty].
|
||
|
||
// Banks $e0, $e1: all locations potentially affected by the language switches or marked for IO.
|
||
// Alas, separate regions are needed due to the same ROM appearing on both pages.
|
||
for(uint8_t c = 0; c < 2; c++) {
|
||
set_regions(0xe0 + c, {0xc000, 0xc100, 0xc300, 0xc400, 0xc800, 0xd000, 0xe000, 0xffff});
|
||
}
|
||
|
||
// [Banks $e2–[ROM start]: empty].
|
||
|
||
// ROM banks: directly mapped to ROM.
|
||
const uint8_t rom_bank_count = uint8_t(rom.size() >> 16);
|
||
const uint8_t first_rom_bank = uint8_t(0x100 - rom_bank_count);
|
||
const uint8_t rom_region = region();
|
||
for(uint8_t c = 0; c < rom_bank_count; ++c) {
|
||
set_region(first_rom_bank + c, 0x0000, 0xffff, rom_region);
|
||
}
|
||
|
||
// Apply proper storage to those banks.
|
||
auto set_storage = [this](uint32_t address, const uint8_t *read, uint8_t *write) {
|
||
// Don't allow the reserved null region to be modified.
|
||
assert(region_map[address >> 8]);
|
||
|
||
// Either set or apply a quick bit of testing as to the logic at play.
|
||
auto ®ion = regions[region_map[address >> 8]];
|
||
if(read) read -= address;
|
||
if(write) write -= address;
|
||
if(!region.read) {
|
||
region.read = read;
|
||
region.write = write;
|
||
} else {
|
||
assert(region.read == read);
|
||
assert(region.write == write);
|
||
}
|
||
};
|
||
|
||
// This is highly redundant, but decouples this step from the above.
|
||
for(size_t c = 0; c < 0x800000; c += 0x100) {
|
||
if(c < ram.size() - 128*1024) {
|
||
set_storage(uint32_t(c), &ram[c], &ram[c]);
|
||
}
|
||
}
|
||
uint8_t *const slow_ram = &ram[ram.size() - 0x20000];
|
||
for(size_t c = 0xe00000; c < 0xe20000; c += 0x100) {
|
||
set_storage(uint32_t(c), &slow_ram[c - 0xe00000], &slow_ram[c - 0xe00000]);
|
||
}
|
||
for(uint32_t c = 0; c < uint32_t(rom_bank_count); c++) {
|
||
set_storage((first_rom_bank + c) << 16, &rom[c << 16], nullptr);
|
||
}
|
||
|
||
// TODO: set 1Mhz flags.
|
||
|
||
// Apply initial language/auxiliary state.
|
||
set_card_paging();
|
||
set_zero_page_paging();
|
||
set_main_paging();
|
||
set_shadowing();
|
||
}
|
||
|
||
// MARK: - Live bus access notifications and register access.
|
||
|
||
void set_shadow_register(uint8_t value) {
|
||
const uint8_t diff = value ^ shadow_register_;
|
||
shadow_register_ = value;
|
||
|
||
if(diff & 0x40) { // IO/language-card inhibit.
|
||
set_language_card_paging();
|
||
set_card_paging();
|
||
}
|
||
|
||
if(diff & 0x3f) {
|
||
set_shadowing();
|
||
}
|
||
}
|
||
|
||
uint8_t get_shadow_register() const {
|
||
return shadow_register_;
|
||
}
|
||
|
||
void set_speed_register(uint8_t value) {
|
||
const uint8_t diff = value ^ speed_register_;
|
||
speed_register_ = value;
|
||
if(diff & 0x10) {
|
||
set_shadowing();
|
||
}
|
||
}
|
||
|
||
void set_state_register(uint8_t value) {
|
||
auxiliary_switches_.set_state(value);
|
||
language_card_.set_state(value);
|
||
}
|
||
|
||
uint8_t get_state_register() const {
|
||
return language_card_.get_state() | auxiliary_switches_.get_state();
|
||
}
|
||
|
||
void access(uint16_t address, bool is_read) {
|
||
auxiliary_switches_.access(address, is_read);
|
||
if((address & 0xfff0) == 0xc080) language_card_.access(address, is_read);
|
||
}
|
||
|
||
using AuxiliaryMemorySwitches = Apple::II::AuxiliaryMemorySwitches<MemoryMap>;
|
||
const AuxiliaryMemorySwitches &auxiliary_switches() const {
|
||
return auxiliary_switches_;
|
||
}
|
||
|
||
using LanguageCardSwitches = Apple::II::LanguageCardSwitches<MemoryMap>;
|
||
const LanguageCardSwitches &language_card_switches() const {
|
||
return language_card_;
|
||
}
|
||
|
||
private:
|
||
AuxiliaryMemorySwitches auxiliary_switches_;
|
||
LanguageCardSwitches language_card_;
|
||
friend AuxiliaryMemorySwitches;
|
||
friend LanguageCardSwitches;
|
||
|
||
uint8_t shadow_register_ = 0x08;
|
||
uint8_t speed_register_ = 0x00;
|
||
|
||
// MARK: - Memory banking.
|
||
|
||
void set_language_card_paging() {
|
||
const auto language_state = language_card_.state();
|
||
const auto zero_state = auxiliary_switches_.zero_state();
|
||
const bool inhibit_banks0001 = shadow_register_ & 0x40;
|
||
|
||
auto apply = [&language_state, &zero_state, this](uint32_t bank_base, uint8_t *ram) {
|
||
// All references below are to 0xc000, 0xd000 and 0xe000 but should
|
||
// work regardless of bank.
|
||
|
||
// This assumes bank 1 is the one before bank 2 when RAM is linear.
|
||
uint8_t *const lower_ram_bank = ram - (language_state.bank1 ? 0x1000 : 0x0000);
|
||
|
||
// Crib the ROM pointer from a page it's always visible on.
|
||
const uint8_t *const rom = ®ions[region_map[0xffd0]].read[0xffd000] - ((bank_base << 8) + 0xd000);
|
||
|
||
auto &d0_region = regions[region_map[bank_base | 0xd0]];
|
||
d0_region.read = language_state.read ? lower_ram_bank : rom;
|
||
d0_region.write = language_state.write ? nullptr : lower_ram_bank;
|
||
|
||
auto &e0_region = regions[region_map[bank_base | 0xe0]];
|
||
e0_region.read = language_state.read ? ram : rom;
|
||
e0_region.write = language_state.write ? nullptr : ram;
|
||
|
||
// Assert assumptions made above re: memory layout.
|
||
assert(region_map[bank_base | 0xd0] + 1 == region_map[bank_base | 0xe0]);
|
||
assert(region_map[bank_base | 0xe0] == region_map[bank_base | 0xff]);
|
||
};
|
||
auto set_no_card = [this](uint32_t bank_base) {
|
||
auto &d0_region = regions[region_map[bank_base | 0xd0]];
|
||
d0_region.read = ram_base;
|
||
d0_region.write = ram_base;
|
||
|
||
auto &e0_region = regions[region_map[bank_base | 0xe0]];
|
||
e0_region.read = ram_base;
|
||
e0_region.write = ram_base;
|
||
};
|
||
|
||
if(inhibit_banks0001) {
|
||
set_no_card(0x0000);
|
||
set_no_card(0x0100);
|
||
} else {
|
||
apply(0x0000, zero_state ? &ram_base[0x10000] : ram_base);
|
||
apply(0x0100, ram_base);
|
||
}
|
||
|
||
uint8_t *const e0_ram = regions[region_map[0xe000]].write;
|
||
apply(0xe000, e0_ram);
|
||
apply(0xe100, e0_ram);
|
||
}
|
||
|
||
void set_card_paging() {
|
||
const bool inhibit_banks0001 = shadow_register_ & 0x40;
|
||
const auto state = auxiliary_switches_.card_state();
|
||
|
||
auto apply = [&state, this](uint32_t bank_base) {
|
||
auto &c0_region = regions[region_map[bank_base | 0xc0]];
|
||
auto &c1_region = regions[region_map[bank_base | 0xc1]];
|
||
auto &c3_region = regions[region_map[bank_base | 0xc3]];
|
||
auto &c4_region = regions[region_map[bank_base | 0xc4]];
|
||
auto &c8_region = regions[region_map[bank_base | 0xc8]];
|
||
|
||
const uint8_t *const rom = ®ions[region_map[0xffd0]].read[0xffc100] - ((bank_base << 8) + 0xc100);
|
||
|
||
// This is applied dynamically as it may be added or lost in banks $00 and $01.
|
||
c0_region.flags |= Region::IsIO;
|
||
|
||
#define apply_region(flag, region) \
|
||
if(flag) { \
|
||
region.read = rom; \
|
||
region.flags &= ~Region::IsIO; \
|
||
} else { \
|
||
region.flags |= Region::IsIO; \
|
||
}
|
||
|
||
apply_region(state.region_C1_C3, c1_region);
|
||
apply_region(state.region_C3, c3_region);
|
||
apply_region(state.region_C4_C8, c4_region);
|
||
apply_region(state.region_C8_D0, c8_region);
|
||
|
||
#undef apply_region
|
||
|
||
// Sanity checks.
|
||
assert(region_map[bank_base | 0xc1] == region_map[bank_base | 0xc0]+1);
|
||
assert(region_map[bank_base | 0xc3] == region_map[bank_base | 0xc1]+1);
|
||
assert(region_map[bank_base | 0xc4] == region_map[bank_base | 0xc3]+1);
|
||
assert(region_map[bank_base | 0xc8] == region_map[bank_base | 0xc4]+1);
|
||
assert(region_map[bank_base | 0xd0] == region_map[bank_base | 0xc8]+1);
|
||
};
|
||
|
||
if(inhibit_banks0001) {
|
||
// Set no IO in the Cx00 range for banks $00 and $01, just
|
||
// regular RAM (or possibly auxiliary).
|
||
const auto auxiliary_state = auxiliary_switches_.main_state();
|
||
for(uint8_t region = region_map[0x00c0]; region < region_map[0x00d0]; region++) {
|
||
regions[region].read = auxiliary_state.base.read ? &ram_base[0x10000] : ram_base;
|
||
regions[region].write = auxiliary_state.base.write ? &ram_base[0x10000] : ram_base;
|
||
regions[region].flags &= ~Region::IsIO;
|
||
}
|
||
for(uint8_t region = region_map[0x01c0]; region < region_map[0x01d0]; region++) {
|
||
regions[region].read = regions[region].write = ram_base;
|
||
regions[region].flags &= ~Region::IsIO;
|
||
}
|
||
} else {
|
||
// Obey the card state for banks $00 and $01.
|
||
apply(0x0000);
|
||
apply(0x0100);
|
||
}
|
||
|
||
// Obey the card state for banks $e0 and $e1.
|
||
apply(0xe000);
|
||
apply(0xe100);
|
||
}
|
||
|
||
void set_zero_page_paging() {
|
||
// Affects bank $00 only, and should be a single region.
|
||
auto ®ion = regions[region_map[0]];
|
||
region.read = region.write = auxiliary_switches_.zero_state() ? &ram_base[0x10000] : ram_base;
|
||
assert(region_map[0x0000]+1 == region_map[0x0002]);
|
||
|
||
// Switching to or from auxiliary RAM potentially affects the language
|
||
// and regular card areas.
|
||
set_card_paging();
|
||
set_language_card_paging();
|
||
}
|
||
|
||
void set_shadowing() {
|
||
const bool inhibit_all_pages = !(speed_register_ & 0x10);
|
||
|
||
// Disables shadowing for the region starting from @c zone if @c flag is true;
|
||
// otherwise enables it.
|
||
#define apply(flag, zone) \
|
||
if(flag) { \
|
||
regions[region_map[zone]].flags &= ~Region::IsShadowed; \
|
||
} else { \
|
||
regions[region_map[zone]].flags |= Region::IsShadowed; \
|
||
}
|
||
|
||
printf("Shadowing: %02x\n", shadow_register_);
|
||
|
||
// Relevant bits:
|
||
//
|
||
// b5: inhibit shadowing, text page 2 [if ROM 03; as if always set otherwise]
|
||
// b4: inhibit shadowing, auxiliary high-res graphics
|
||
// b3: inhibit shadowing, super high-res graphics
|
||
// b2: inhibit shadowing, high-res graphics page 2
|
||
// b1: inhibit shadowing, high-res graphics page 1
|
||
// b0: inhibit shadowing, text page 1
|
||
//
|
||
// The interpretations of how the overlapping high-res and super high-res inhibit
|
||
// bits apply used below is taken from The Apple IIgs Technical Reference, P. 178.
|
||
|
||
// Text Page 1, main and auxiliary — $0400–$0800.
|
||
apply(shadow_register_ & 0x01, 0x0004);
|
||
apply(shadow_register_ & 0x01, 0x0104);
|
||
apply((shadow_register_ & 0x01) || inhibit_all_pages, 0x0204); // All other pages uses the same shadowing flags.
|
||
apply((shadow_register_ & 0x01) || inhibit_all_pages, 0x0304);
|
||
assert(region_map[0x0008] == region_map[0x0004]+1);
|
||
assert(region_map[0x0108] == region_map[0x0104]+1);
|
||
assert(region_map[0x0208] == region_map[0x0204]+1);
|
||
assert(region_map[0x0308] == region_map[0x0304]+1);
|
||
|
||
// Text Page 2, main and auxiliary — 0x0800–0x0c00.
|
||
// TODO: on a ROM03 machine only.
|
||
apply(shadow_register_ & 0x20, 0x0008);
|
||
apply(shadow_register_ & 0x20, 0x0108);
|
||
apply((shadow_register_ & 0x20) || inhibit_all_pages, 0x0208);
|
||
apply((shadow_register_ & 0x20) || inhibit_all_pages, 0x0308);
|
||
assert(region_map[0x000c] == region_map[0x0008]+1);
|
||
assert(region_map[0x010c] == region_map[0x0108]+1);
|
||
assert(region_map[0x020c] == region_map[0x0208]+1);
|
||
assert(region_map[0x030c] == region_map[0x0308]+1);
|
||
|
||
// Hi-res graphics Page 1, main and auxiliary — $2000–$4000;
|
||
// also part of the super high-res graphics page.
|
||
//
|
||
// Test applied: both the graphics page inhibit and, on odd
|
||
// pages, the super high-res inhibit must be applied to inhibit
|
||
// this area.
|
||
apply(shadow_register_ & 0x02, 0x0020);
|
||
apply((shadow_register_ & 0x12) && (shadow_register_ & 0x08), 0x0120);
|
||
apply((shadow_register_ & 0x02) || inhibit_all_pages, 0x0220);
|
||
apply(((shadow_register_ & 0x12) && (shadow_register_ & 0x08)) || inhibit_all_pages, 0x0320);
|
||
assert(region_map[0x0040] == region_map[0x0020]+1);
|
||
assert(region_map[0x0140] == region_map[0x0120]+1);
|
||
assert(region_map[0x0240] == region_map[0x0220]+1);
|
||
assert(region_map[0x0340] == region_map[0x0320]+1);
|
||
|
||
// Hi-res graphics Page 2, main and auxiliary — $4000–$6000;
|
||
// also part of the super high-res graphics page.
|
||
//
|
||
// Test applied: both the graphics page inhibit and, on odd
|
||
// pages, the super high-res inhibit must be applied to inhibit
|
||
// this area.
|
||
apply(shadow_register_ & 0x04, 0x0040);
|
||
apply((shadow_register_ & 0x14) && (shadow_register_ & 0x08), 0x0140);
|
||
apply((shadow_register_ & 0x04) || inhibit_all_pages, 0x0240);
|
||
apply(((shadow_register_ & 0x14) && (shadow_register_ & 0x08)) || inhibit_all_pages, 0x0340);
|
||
assert(region_map[0x0060] == region_map[0x0040]+1);
|
||
assert(region_map[0x0160] == region_map[0x0140]+1);
|
||
assert(region_map[0x0260] == region_map[0x0240]+1);
|
||
assert(region_map[0x0360] == region_map[0x0340]+1);
|
||
|
||
// Residue of Super Hi-Res — $6000–$a000 (odd pages only).
|
||
apply(shadow_register_ & 0x08, 0x0160);
|
||
apply((shadow_register_ & 0x08) || inhibit_all_pages, 0x0360);
|
||
assert(region_map[0x01a0] == region_map[0x0160]+1);
|
||
assert(region_map[0x03a0] == region_map[0x0360]+1);
|
||
|
||
#undef apply
|
||
}
|
||
|
||
void set_main_paging() {
|
||
const auto state = auxiliary_switches_.main_state();
|
||
|
||
#define set(page, flags) {\
|
||
auto ®ion = regions[region_map[page]]; \
|
||
region.read = flags.read ? &ram_base[0x10000] : ram_base; \
|
||
region.write = flags.write ? &ram_base[0x10000] : ram_base; \
|
||
}
|
||
|
||
set(0x02, state.base);
|
||
set(0x08, state.base);
|
||
set(0x40, state.base);
|
||
set(0x04, state.region_04_08);
|
||
set(0x20, state.region_20_40);
|
||
|
||
#undef set
|
||
// This also affects shadowing flags, if shadowing is enabled at all,
|
||
// and might affect RAM in the IO area of bank $00 because the language
|
||
// card can be inhibited on a IIgs.
|
||
set_shadowing();
|
||
set_card_paging();
|
||
}
|
||
|
||
uint8_t shadow_throwaway_;
|
||
|
||
public:
|
||
// Memory layout here is done via double indirection; the main loop should:
|
||
// (i) use the top two bytes of the address to get an index from memory_map_; and
|
||
// (ii) use that to index the memory_regions table.
|
||
//
|
||
// Pointers are eight bytes at the time of writing, so the extra level of indirection
|
||
// reduces what would otherwise be a 1.25mb table down to not a great deal more than 64kb.
|
||
std::array<uint8_t, 65536> region_map{};
|
||
uint8_t *ram_base = nullptr;
|
||
uint8_t *shadow_base[2] = {&shadow_throwaway_, nullptr};
|
||
const int shadow_modulo[2] = {1, 128*1024};
|
||
|
||
struct Region {
|
||
uint8_t *write = nullptr;
|
||
const uint8_t *read = nullptr;
|
||
uint8_t flags = 0;
|
||
|
||
enum Flag: uint8_t {
|
||
IsShadowed = 1 << 0, // Writes should be shadowed to [end of RAM - 128kb + base offset].
|
||
Is1Mhz = 1 << 1, // Both reads and writes should be synchronised with the 1Mhz clock.
|
||
IsIO = 1 << 2, // Indicates that this region should be checked for soft switches, registers, etc;
|
||
// usurps the shadowed flags.
|
||
};
|
||
};
|
||
std::array<Region, 64> regions; // The assert above ensures that this is large enough; there's no
|
||
// doctrinal reason for it to be whatever size it is now, just
|
||
// adjust as required.
|
||
};
|
||
|
||
// TODO: branching below on region.read/write is predicated on the idea that extra scratch space
|
||
// would be less efficient. Verify that?
|
||
|
||
#define MemoryMapRegion(map, address) map.regions[map.region_map[address >> 8]]
|
||
#define MemoryMapRead(region, address, value) *value = region.read ? region.read[address] : 0xff
|
||
#define MemoryMapWrite(map, region, address, value) \
|
||
if(region.write) { \
|
||
region.write[address] = *value; \
|
||
const auto is_shadowed = region.flags & MemoryMap::Region::IsShadowed; \
|
||
map.shadow_base[is_shadowed][(®ion.write[address] - map.ram_base) % map.shadow_modulo[is_shadowed]] = *value; \
|
||
}
|
||
|
||
// Quick notes on ::IsShadowed contortions:
|
||
//
|
||
// The objective is to support shadowing:
|
||
// 1. without storing a whole extra pointer, and such that the shadowing flags are orthogonal to the current auxiliary memory settings;
|
||
// 2. in such a way as to support shadowing both in banks $00/$01 and elsewhere; and
|
||
// 3. to do so without introducing too much in the way of branching.
|
||
//
|
||
// Hence the implemented solution: if shadowing is enabled then use the distance from the start of physical RAM
|
||
// modulo 128k indexed into the bank $e0/$e1 RAM.
|
||
//
|
||
// With a further twist: the modulo and pointer are indexed on ::IsShadowed to eliminate a branch even on that.
|
||
|
||
}
|
||
}
|
||
|
||
#endif /* MemoryMap_h */
|