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Implements the ROM version of fast loading.

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This commit is contained in:
Thomas Harte 2021-03-22 19:04:38 -04:00
parent 4a12d7086d
commit 3ef2715eee
1 changed files with 56 additions and 1 deletions
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57
Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
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@ -24,6 +24,9 @@
#include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
#include "../../../Storage/Tape/Tape.hpp"
#include "../../../Storage/Tape/Parsers/Spectrum.hpp"
#include "../../../Analyser/Static/ZXSpectrum/Target.hpp"
#include "../../Utility/MemoryFuzzer.hpp"
@ -163,6 +166,16 @@ template<Model model> class ConcreteMachine:
break;
case PartialMachineCycle::ReadOpcode:
// Fast loading: ROM version.
//
// The below patches over the 'LD-BYTES' routine from the 48kb ROM.
if(use_fast_tape_hack_ && address == 0x0556 && read_pointers_[0] == &rom_[0xc000]) {
if(perform_rom_ld_bytes()) {
*cycle.value = 0xc9; // i.e. RET.
break;
}
}
case PartialMachineCycle::Read:
*cycle.value = read_pointers_[address >> 14][address];
break;
@ -493,8 +506,50 @@ template<Model model> class ConcreteMachine:
int recent_tape_hits_ = 0;
bool allow_fast_tape_hack_ = false;
bool use_fast_tape_hack_ = false;
void set_use_fast_tape() {
// TODO.
use_fast_tape_hack_ = allow_fast_tape_hack_ && tape_player_.has_tape();
}
// Reimplements the 'LD-BYTES' routine, as documented at
// https://skoolkid.github.io/rom/asm/0556.html i.e.
//
// In:
// A: 0x00 or 0xff for block type;
// F: carry set if loading, clear if verifying;
// DE: block length;
// IX: start address.
//
// Out:
// F: carry set for success, clear for error.
bool perform_rom_ld_bytes() {
using Parser = Storage::Tape::ZXSpectrum::Parser;
Parser parser(Parser::MachineType::ZXSpectrum);
using Register = CPU::Z80::Register;
uint8_t flags = uint8_t(z80_.get_value_of_register(Register::Flags));
if(!(flags & 1)) return false;
const uint8_t block_type = uint8_t(z80_.get_value_of_register(Register::A));
const auto block = parser.find_block(tape_player_.get_tape());
if(!block || block_type != (*block).type) return false;
uint16_t length = z80_.get_value_of_register(Register::DE);
uint16_t target = z80_.get_value_of_register(Register::IX);
while(length--) {
auto next = parser.get_byte(tape_player_.get_tape());
if(!next) {
flags &= ~1;
break;
}
write_pointers_[target >> 14][target] = *next;
++target;
}
z80_.set_value_of_register(Register::Flags, flags);
return true;
}
};