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Made a first attempt at ZX81 emulation.

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This commit is contained in:
Thomas Harte 2017-06-13 21:25:55 -04:00
parent 1e975859c2
commit 76a64d13a0
2 changed files with 36 additions and 22 deletions
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56
Machines/ZX8081/ZX8081.cpp
View File

@ -20,6 +20,7 @@ namespace {
Machine::Machine() :
vsync_(false),
hsync_(false),
nmi_is_enabled_(false),
tape_player_(ZX8081ClockRate) {
set_clock_rate(ZX8081ClockRate);
tape_player_.set_motor_control(true);
@ -27,30 +28,34 @@ Machine::Machine() :
}
int Machine::perform_machine_cycle(const CPU::Z80::MachineCycle &cycle) {
const int vsync_length = 16;
int wait_cycles = 0;
int previous_counter = horizontal_counter_;
horizontal_counter_ += cycle.length;
if(is_zx81_) {
} else {
const int vsync_start_cycle = 13;
const int vsync_end_cycle = vsync_start_cycle + vsync_length;
if(previous_counter < vsync_start_cycle && horizontal_counter_ >= vsync_start_cycle) {
video_->run_for_cycles(vsync_start_cycle - previous_counter);
set_hsync(true);
video_->run_for_cycles(horizontal_counter_ - vsync_start_cycle);
} else if(previous_counter < vsync_end_cycle && horizontal_counter_ >= vsync_end_cycle) {
video_->run_for_cycles(vsync_end_cycle - previous_counter);
set_hsync(false);
video_->run_for_cycles(horizontal_counter_ - vsync_end_cycle);
} else {
video_->run_for_cycles(cycle.length);
if(previous_counter < vsync_start_cycle_ && horizontal_counter_ >= vsync_start_cycle_) {
video_->run_for_cycles(vsync_start_cycle_ - previous_counter);
set_hsync(true);
if(nmi_is_enabled_) {
set_non_maskable_interrupt_line(true);
if(get_halt_line()) {
wait_cycles = vsync_start_cycle_ - horizontal_counter_;
}
}
video_->run_for_cycles(horizontal_counter_ - vsync_start_cycle_ + wait_cycles);
} else if(previous_counter < vsync_end_cycle_ && horizontal_counter_ >= vsync_end_cycle_) {
video_->run_for_cycles(vsync_end_cycle_ - previous_counter);
set_hsync(false);
if(nmi_is_enabled_) set_non_maskable_interrupt_line(false);
video_->run_for_cycles(horizontal_counter_ - vsync_end_cycle_);
} else {
video_->run_for_cycles(cycle.length);
}
// tape_player_.run_for_cycles(cycle.length);
horizontal_counter_ += wait_cycles;
if(is_zx81_) horizontal_counter_ %= 207;
// tape_player_.run_for_cycles(cycle.length + wait_cycles);
uint16_t refresh = 0;
uint16_t address = cycle.address ? *cycle.address : 0;
@ -58,6 +63,12 @@ int Machine::perform_machine_cycle(const CPU::Z80::MachineCycle &cycle) {
case CPU::Z80::BusOperation::Output:
set_vsync(false);
line_counter_ = 0;
switch(address & 7) {
default: break;
case 0x5: nmi_is_enabled_ = false; break;
case 0x6: nmi_is_enabled_ = is_zx81_; break;
}
break;
case CPU::Z80::BusOperation::Input: {
@ -77,15 +88,12 @@ int Machine::perform_machine_cycle(const CPU::Z80::MachineCycle &cycle) {
} break;
case CPU::Z80::BusOperation::Interrupt:
// set_hsync(true);
line_counter_ = (line_counter_ + 1) & 7;
*cycle.value = 0xff;
horizontal_counter_ = 0; // TODO: more than this?
horizontal_counter_ = 0;
break;
case CPU::Z80::BusOperation::ReadOpcode:
// set_hsync(false);
// The ZX80 and 81 signal an interrupt while refresh is active and bit 6 of the refresh
// address is low. The Z80 signals a refresh, providing the refresh address during the
// final two cycles of an opcode fetch. Therefore communicate a transient signalling
@ -137,7 +145,7 @@ int Machine::perform_machine_cycle(const CPU::Z80::MachineCycle &cycle) {
default: break;
}
return 0;
return wait_cycles;
}
void Machine::flush() {
@ -170,10 +178,14 @@ void Machine::configure_as_target(const StaticAnalyser::Target &target) {
rom_ = zx81_rom_;
tape_trap_address_ = 0x37c;
tape_return_address_ = 0x380;
vsync_start_cycle_ = 13;
vsync_end_cycle_ = 33;
} else {
rom_ = zx80_rom_;
tape_trap_address_ = 0x220;
tape_return_address_ = 0x248;
vsync_start_cycle_ = 16;
vsync_end_cycle_ = 32;
}
rom_mask_ = (uint16_t)(rom_.size() - 1);

2
Machines/ZX8081/ZX8081.hpp
View File

@ -87,6 +87,8 @@ class Machine:
int horizontal_counter_;
bool is_zx81_;
bool nmi_is_enabled_;
int vsync_start_cycle_, vsync_end_cycle_;
};
}