From 76a64d13a0bf0f09086ce437268751b2fc21a629 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 13 Jun 2017 21:25:55 -0400
Subject: [PATCH] Made a first attempt at ZX81 emulation.
---
Machines/ZX8081/ZX8081.cpp | 56 +++++++++++++++++++++++---------------
Machines/ZX8081/ZX8081.hpp | 2 ++
2 files changed, 36 insertions(+), 22 deletions(-)
diff --git a/Machines/ZX8081/ZX8081.cpp b/Machines/ZX8081/ZX8081.cpp
index ace532409..a1ab3ecd5 100644
--- a/Machines/ZX8081/ZX8081.cpp
+++ b/Machines/ZX8081/ZX8081.cpp
@@ -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);
diff --git a/Machines/ZX8081/ZX8081.hpp b/Machines/ZX8081/ZX8081.hpp
index c921fd79a..5778b85fe 100644
--- a/Machines/ZX8081/ZX8081.hpp
+++ b/Machines/ZX8081/ZX8081.hpp
@@ -87,6 +87,8 @@ class Machine:
int horizontal_counter_;
bool is_zx81_;
+ bool nmi_is_enabled_;
+ int vsync_start_cycle_, vsync_end_cycle_;
};
}