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627 lines
19 KiB
C++
627 lines
19 KiB
C++
//
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// Nick.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/06/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "Nick.hpp"
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#include <cstdio>
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namespace {
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uint16_t mapped_colour(uint8_t source) {
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// On the Enterprise, red and green are 3-bit quantities; blue is a 2-bit quantity.
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int red = ((source&0x01) << 2) | ((source&0x08) >> 2) | ((source&0x40) >> 6);
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int green = ((source&0x02) << 1) | ((source&0x10) >> 3) | ((source&0x80) >> 7);
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int blue = ((source&0x04) >> 1) | ((source&0x20) >> 5);
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assert(red <= 7);
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assert(green <= 7);
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assert(blue <= 3);
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red = (red << 1) + (red >> 3);
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green = (green << 1) + (green >> 3);
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blue = (blue << 2) + blue;
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assert(red <= 15);
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assert(green <= 15);
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assert(blue <= 15);
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// Duplicate bits where necessary to map to a full 4-bit range per channel.
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const uint8_t parts[2] = {
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uint8_t(
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red
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),
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uint8_t(
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(green << 4) + blue
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)
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};
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return *reinterpret_cast<const uint16_t *>(parts);
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}
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}
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using namespace Enterprise;
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Nick::Nick(const uint8_t *ram) :
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crt_(57*16, 16, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4),
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ram_(ram) {
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// Just use RGB for now.
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set_display_type(Outputs::Display::DisplayType::RGB);
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// Crop to the centre 90% of the display.
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crt_.set_visible_area(Outputs::Display::Rect(0.05f, 0.05f, 0.9f, 0.9f));
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}
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void Nick::write(uint16_t address, uint8_t value) {
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switch(address & 3) {
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case 0:
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// Ignored: everything to do with external colour.
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for(int c = 0; c < 8; c++) {
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palette_[c + 8] = mapped_colour(uint8_t(((value & 0x1f) << 3) + c));
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}
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break;
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case 1:
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if(output_type_ == OutputType::Border) {
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set_output_type(OutputType::Border, true);
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}
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border_colour_ = mapped_colour(value);
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break;
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case 2:
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line_parameter_base_ = uint16_t((line_parameter_base_ & 0xf000) | (value << 4));
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break;
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case 3:
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line_parameter_base_ = uint16_t((line_parameter_base_ & 0x0ff0) | (value << 12));
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// Still a mystery to me: the exact meaning of the top two bits here. For now
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// just treat a 0 -> 1 transition of the MSB as a forced frame restart.
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if((value^line_parameter_control_) & value & 0x80) {
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// For now: just force this to be the final line of this mode block.
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// I'm unclear whether I should also reset the horizontal counter
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// (i.e. completely abandon current video phase).
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lines_remaining_ = 0xff;
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should_reload_line_parameters_ = true;
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}
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line_parameter_control_ = value & 0xc0;
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break;
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}
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}
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uint8_t Nick::read() {
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return last_read_;
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}
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Cycles Nick::get_time_until_z80_slot(Cycles after_period) const {
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// Place Z80 accesses in the first six cycles in each sixteen-cycle window.
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// That models video accesses as being the final ten. Which has the net effect
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// of responding to the line parameter table interrupt flag as soon as it's
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// loaded.
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// Assumed below: the Z80 can start its final cycle anywhere in the first three
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// of the permitted six.
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const int offset = (horizontal_counter_ + after_period.as<int>()) & 15;
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if(offset < 3) {
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return 0;
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} else {
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return 16 - offset;
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}
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}
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void Nick::run_for(Cycles duration) {
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constexpr int line_length = 912;
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#define add_window(x) \
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line_data_pointer_[0] += is_sync_or_pixels_ * line_data_per_column_increments_[0] * (x); \
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line_data_pointer_[1] += is_sync_or_pixels_ * line_data_per_column_increments_[1] * (x); \
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window += x; \
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if(window != 57 && window == left_margin_) is_sync_or_pixels_ = true; \
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if(window != 57 && window == right_margin_) is_sync_or_pixels_ = false;
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int clocks_remaining = duration.as<int>();
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while(clocks_remaining) {
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// Determine how many cycles are left this line.
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const int clocks_this_line = std::min(clocks_remaining, line_length - horizontal_counter_);
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// Convert that into a [start/current] and end window.
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int window = horizontal_counter_ >> 4;
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const int end_window = (horizontal_counter_ + clocks_this_line) >> 4;
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// Advance the line counters.
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clocks_remaining -= clocks_this_line;
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horizontal_counter_ = (horizontal_counter_ + clocks_this_line) % line_length;
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// Do nothing if a window boundary isn't crossed.
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if(window == end_window) continue;
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// HSYNC is signalled for four windows at the start of the line.
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// I currently believe this happens regardless of Vsync mode.
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if(!window) {
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set_output_type(OutputType::Sync);
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// There's no increment to get to 0, it happens when the horizontal_counter_
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// is reset. So test for active bit effect manually.
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if(!left_margin_) is_sync_or_pixels_ = true;
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if(!right_margin_) is_sync_or_pixels_ = false;
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}
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// Default to noting read.
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last_read_ = 0xff;
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while(window < 4 && window < end_window) {
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if(should_reload_line_parameters_) {
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switch(window) {
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// First slot: line count, mode and interrupt flag.
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case 0:
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// Byte 0: lines remaining.
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lines_remaining_ = ram_[line_parameter_pointer_];
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// Byte 1: current interrupt output plus graphics modes...
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last_read_ = ram_[line_parameter_pointer_ + 1];
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// Set the new interrupt line output.
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interrupt_line_ = ram_[line_parameter_pointer_ + 1] & 0x80;
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// Determine the mode and depth, and hence the column size.
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mode_ = Mode((ram_[line_parameter_pointer_ + 1] >> 1)&7);
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bpp_ = 1 << ((ram_[line_parameter_pointer_ + 1] >> 5)&3);
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switch(mode_) {
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default:
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case Mode::Pixel:
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column_size_ = 16 / bpp_;
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line_data_per_column_increments_[0] = 2;
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line_data_per_column_increments_[1] = 0;
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break;
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case Mode::LPixel:
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case Mode::CH64:
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case Mode::CH128:
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case Mode::CH256:
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column_size_ = 8 / bpp_;
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line_data_per_column_increments_[0] = 1;
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line_data_per_column_increments_[1] = 0;
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break;
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case Mode::Attr:
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column_size_ = 8;
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line_data_per_column_increments_[0] = 1;
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line_data_per_column_increments_[1] = 1;
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break;
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}
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vres_ = ram_[line_parameter_pointer_ + 1] & 0x10;
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reload_line_parameter_pointer_ = ram_[line_parameter_pointer_ + 1] & 0x01;
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break;
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// Second slot: margins and ALT/IND bits.
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case 1:
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// Determine the margins.
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left_margin_ = ram_[line_parameter_pointer_ + 2] & 0x3f;
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right_margin_ = ram_[line_parameter_pointer_ + 3] & 0x3f;
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last_read_ = ram_[line_parameter_pointer_ + 3];
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// Set up the alternative palettes,
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switch(mode_) {
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default:
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break;
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// NB: LSBALT/MSBALT and ALTIND0/ALTIND1 appear to have opposite effects on palette selection.
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case Mode::Pixel:
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case Mode::LPixel: {
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const uint8_t flags = ram_[line_parameter_pointer_ + 2];
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// Use MSBALT and LSBALT to pick the alt_ind_palettes.
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//
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// LSBALT = b6 of params[2], if set => character codes with bit 6 set should use palette indices 4... instead of 0... .
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// MSBALT = b7 of params[2], if set => character codes with bit 7 set should use palette indices 2 and 3.
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two_colour_mask_ = 0xff &~ (((flags&0x80) >> 7) | ((flags&0x40) << 1));
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alt_ind_palettes[0] = palette_;
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alt_ind_palettes[2] = alt_ind_palettes[0] + ((flags & 0x80) ? 2 : 0);
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alt_ind_palettes[1] = alt_ind_palettes[0] + ((flags & 0x40) ? 4 : 0);
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alt_ind_palettes[3] = alt_ind_palettes[2] + ((flags & 0x40) ? 4 : 0);
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} break;
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case Mode::CH64:
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case Mode::CH128:
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case Mode::CH256: {
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const uint8_t flags = ram_[line_parameter_pointer_ + 3];
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// Use ALTIND0 and ALTIND1 to pick the alt_ind_palettes.
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//
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// ALTIND1 = b6 of params[3], if set => character codes with bit 7 set should use palette indices 2 and 3.
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// ALTIND0 = b7 of params[3], if set => character codes with bit 6 set should use palette indices 4... instead of 0... .
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alt_ind_palettes[0] = palette_;
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alt_ind_palettes[2] = alt_ind_palettes[0] + ((flags & 0x40) ? 2 : 0);
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alt_ind_palettes[1] = alt_ind_palettes[0] + ((flags & 0x80) ? 4 : 0);
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alt_ind_palettes[3] = alt_ind_palettes[2] + ((flags & 0x80) ? 4 : 0);
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} break;
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}
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break;
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// Third slot: Line data pointer 1.
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case 2:
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start_line_data_pointer_[0] = ram_[line_parameter_pointer_ + 4];
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start_line_data_pointer_[0] |= ram_[line_parameter_pointer_ + 5] << 8;
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line_data_pointer_[0] = start_line_data_pointer_[0];
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last_read_ = ram_[line_parameter_pointer_ + 5];
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break;
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// Fourth slot: Line data pointer 2.
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case 3:
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start_line_data_pointer_[1] = ram_[line_parameter_pointer_ + 6];
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start_line_data_pointer_[1] |= ram_[line_parameter_pointer_ + 7] << 8;
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line_data_pointer_[1] = start_line_data_pointer_[1];
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last_read_ = ram_[line_parameter_pointer_ + 7];
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break;
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}
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}
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++output_duration_;
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add_window(1);
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}
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if(window == 4) {
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if(mode_ == Mode::Vsync) {
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set_output_type(is_sync_or_pixels_ ? OutputType::Sync : OutputType::Blank);
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} else {
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set_output_type(OutputType::Blank);
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}
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}
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// Deal with vsync mode out here.
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if(mode_ == Mode::Vsync) {
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if(window >= 4) {
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while(window < end_window) {
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// Skip straight to the next event.
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int next_event = end_window;
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if(window < left_margin_) next_event = std::min(next_event, left_margin_);
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if(window < right_margin_) next_event = std::min(next_event, right_margin_);
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output_duration_ += next_event - window;
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add_window(next_event - window);
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set_output_type(is_sync_or_pixels_ ? OutputType::Sync : OutputType::Blank);
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}
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}
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} else {
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// If present then the colour burst is output for the period from
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// the start of window 6 to the end of window 10.
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//
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// The first 8 palette entries also need to be fetched here.
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while(window < first_pixel_window_ && window < end_window) {
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if(window == 6) {
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set_output_type(OutputType::ColourBurst);
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}
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if(should_reload_line_parameters_ && window < 8) {
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const int base = (window - 4) << 1;
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assert(base < 7);
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palette_[base] = mapped_colour(ram_[line_parameter_pointer_ + base + 8]);
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palette_[base + 1] = mapped_colour(ram_[line_parameter_pointer_ + base + 9]);
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last_read_ = ram_[line_parameter_pointer_ + base + 9];
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}
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++output_duration_;
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add_window(1);
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}
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if(window >= first_pixel_window_) {
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if(window == first_pixel_window_) {
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set_output_type(is_sync_or_pixels_ ? OutputType::Pixels : OutputType::Border);
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}
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while(window < end_window) {
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int next_event = end_window;
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if(window < left_margin_) next_event = std::min(next_event, left_margin_);
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if(window < right_margin_) next_event = std::min(next_event, right_margin_);
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if(is_sync_or_pixels_) {
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#define DispatchBpp(func) \
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switch(bpp_) { \
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default: \
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case 1: func(1)(pixel_pointer_, output_duration); break; \
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case 2: func(2)(pixel_pointer_, output_duration); break; \
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case 4: func(4)(pixel_pointer_, output_duration); break; \
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case 8: func(8)(pixel_pointer_, output_duration); break; \
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}
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#define pixel(x) output_pixel<x, false>
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#define lpixel(x) output_pixel<x, true>
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#define ch256(x) output_character<x, 8>
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#define ch128(x) output_character<x, 7>
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#define ch64(x) output_character<x, 6>
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#define attr(x) output_attributed<x>
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int columns_remaining = next_event - window;
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while(columns_remaining) {
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if(!pixel_pointer_) {
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if(output_duration_) {
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set_output_type(OutputType::Pixels, true);
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}
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pixel_pointer_ = allocated_pointer_ = reinterpret_cast<uint16_t *>(crt_.begin_data(allocation_size));
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}
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if(allocated_pointer_) {
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const int output_duration = std::min(columns_remaining, int(allocated_pointer_ + allocation_size - pixel_pointer_) / column_size_);
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switch(mode_) {
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default:
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case Mode::Pixel: DispatchBpp(pixel); break;
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case Mode::LPixel: DispatchBpp(lpixel); break;
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case Mode::CH256: DispatchBpp(ch256); break;
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case Mode::CH128: DispatchBpp(ch128); break;
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case Mode::CH64: DispatchBpp(ch64); break;
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case Mode::Attr: DispatchBpp(attr); break;
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}
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pixel_pointer_ += output_duration * column_size_;
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output_duration_ += output_duration;
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if(pixel_pointer_ - allocated_pointer_ == allocation_size) {
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set_output_type(OutputType::Pixels, true);
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}
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columns_remaining -= output_duration;
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add_window(output_duration);
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} else {
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output_duration_ += columns_remaining;
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add_window(columns_remaining);
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columns_remaining = 0;
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}
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}
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#undef attr
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#undef ch64
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#undef ch128
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#undef ch256
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#undef pixel
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#undef lpixel
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#undef DispatchBpp
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} else {
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output_duration_ += next_event - window;
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add_window(next_event - window);
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}
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set_output_type(is_sync_or_pixels_ ? OutputType::Pixels : OutputType::Border);
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}
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}
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}
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// Check for end of line.
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if(!horizontal_counter_) {
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assert(window == 57);
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++lines_remaining_;
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if(!lines_remaining_) {
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should_reload_line_parameters_ = true;
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// Check for end-of-frame.
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if(reload_line_parameter_pointer_) {
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line_parameter_pointer_ = line_parameter_base_;
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} else {
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line_parameter_pointer_ += 16;
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}
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} else {
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should_reload_line_parameters_ = false;
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}
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// Deal with VRES and other address reloading, dependant upon mode.
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switch(mode_) {
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default: break;
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case Mode::CH64:
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case Mode::CH128:
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case Mode::CH256:
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line_data_pointer_[0] = start_line_data_pointer_[0];
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++line_data_pointer_[1];
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break;
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case Mode::Pixel:
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case Mode::LPixel:
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case Mode::Attr:
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// Reload the pixel or attribute address if VRES is clear.
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if(!vres_) {
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line_data_pointer_[0] = start_line_data_pointer_[0];
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}
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break;
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}
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}
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}
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#undef add_window
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}
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void Nick::set_output_type(OutputType type, bool force_flush) {
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if(type == output_type_ && !force_flush) {
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return;
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}
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if(output_duration_) {
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const int duration = output_duration_ * 16;
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switch(output_type_) {
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case OutputType::Pixels: {
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crt_.output_data(duration, size_t(output_duration_*column_size_));
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pixel_pointer_ = nullptr;
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allocated_pointer_ = nullptr;
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} break;
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case OutputType::Border: crt_.output_level<uint16_t>(duration, border_colour_); break;
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case OutputType::Sync: crt_.output_sync(duration); break;
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case OutputType::Blank: crt_.output_blank(duration); break;
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case OutputType::ColourBurst: crt_.output_colour_burst(duration, 0); break;
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}
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}
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output_duration_ = 0;
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output_type_ = type;
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}
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// MARK: - Sequence points.
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Cycles Nick::next_sequence_point() const {
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constexpr int load_point = 16; // i.e. 16 cycles after the start of the line, the
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// interrupt line may change. That is, after the
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// second byte of the mode line has been read.
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// Any mode line may cause a change in the interrupt output, so as a first blush
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// just always report the time until the end of the mode line.
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if(lines_remaining_ || horizontal_counter_ >= load_point) {
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return Cycles(load_point + (912 - horizontal_counter_) + (0xff - lines_remaining_) * 912);
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} else {
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return Cycles(load_point - horizontal_counter_);
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}
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}
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// MARK: - CRT passthroughs.
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void Nick::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
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crt_.set_scan_target(scan_target);
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}
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Outputs::Display::ScanStatus Nick::get_scaled_scan_status() const {
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return crt_.get_scaled_scan_status();
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}
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void Nick::set_display_type(Outputs::Display::DisplayType display_type) {
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first_pixel_window_ = display_type == Outputs::Display::DisplayType::RGB ? 8 : 10;
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crt_.set_display_type(display_type);
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}
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Outputs::Display::DisplayType Nick::get_display_type() const {
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return crt_.get_display_type();
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}
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// MARK: - Specific pixel outputters.
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|
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|
#define output1bpp(x) \
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target[0] = palette[(x & 0x80) >> 7]; \
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target[1] = palette[(x & 0x40) >> 6]; \
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target[2] = palette[(x & 0x20) >> 5]; \
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|
target[3] = palette[(x & 0x10) >> 4]; \
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|
target[4] = palette[(x & 0x08) >> 3]; \
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|
target[5] = palette[(x & 0x04) >> 2]; \
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|
target[6] = palette[(x & 0x02) >> 1]; \
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|
target[7] = palette[(x & 0x01) >> 0]; \
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|
target += 8
|
|
|
|
#define output2bpp(x) \
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|
target[0] = palette_[((x & 0x80) >> 7) | ((x & 0x08) >> 2)]; \
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|
target[1] = palette_[((x & 0x40) >> 6) | ((x & 0x04) >> 1)]; \
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|
target[2] = palette_[((x & 0x20) >> 5) | ((x & 0x02) >> 0)]; \
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|
target[3] = palette_[((x & 0x10) >> 4) | ((x & 0x01) << 1)]; \
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|
target += 4
|
|
|
|
#define output4bpp(x) \
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|
target[0] = palette_[((x & 0x02) << 2) | ((x & 0x20) >> 3) | ((x & 0x08) >> 2) | ((x & 0x80) >> 7)]; \
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|
target[1] = palette_[((x & 0x01) << 3) | ((x & 0x10) >> 2) | ((x & 0x04) >> 1) | ((x & 0x40) >> 6)]; \
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|
target += 2
|
|
|
|
#define output8bpp(x) \
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|
target[0] = mapped_colour(x); \
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|
++target
|
|
|
|
template <int bpp, bool is_lpixel> void Nick::output_pixel(uint16_t *target, int columns) const {
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|
static_assert(bpp == 1 || bpp == 2 || bpp == 4 || bpp == 8);
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|
|
|
int index = 0;
|
|
for(int c = 0; c < columns; c++) {
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|
uint8_t pixels[2] = {
|
|
ram_[(line_data_pointer_[0] + index) & 0xffff],
|
|
ram_[(line_data_pointer_[0] + index + 1) & 0xffff]
|
|
};
|
|
index += is_lpixel ? 1 : 2;
|
|
last_read_ = pixels[1];
|
|
|
|
switch(bpp) {
|
|
default:
|
|
case 1: {
|
|
const uint16_t *palette = alt_ind_palettes[((pixels[0] >> 6) & 0x02) | (pixels[0]&1)];
|
|
pixels[0] &= two_colour_mask_;
|
|
output1bpp(pixels[0]);
|
|
|
|
if constexpr (!is_lpixel) {
|
|
palette = alt_ind_palettes[((pixels[1] >> 6) & 0x02) | (pixels[1]&1)];
|
|
pixels[1] &= two_colour_mask_;
|
|
output1bpp(pixels[1]);
|
|
}
|
|
} break;
|
|
|
|
case 2:
|
|
output2bpp(pixels[0]);
|
|
if constexpr (!is_lpixel) {
|
|
output2bpp(pixels[1]);
|
|
}
|
|
break;
|
|
|
|
case 4:
|
|
output4bpp(pixels[0]);
|
|
if constexpr (!is_lpixel) {
|
|
output4bpp(pixels[1]);
|
|
}
|
|
break;
|
|
|
|
case 8:
|
|
output8bpp(pixels[0]);
|
|
if constexpr (!is_lpixel) {
|
|
output8bpp(pixels[1]);
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
template <int bpp, int index_bits> void Nick::output_character(uint16_t *target, int columns) const {
|
|
static_assert(bpp == 1 || bpp == 2 || bpp == 4 || bpp == 8);
|
|
|
|
for(int c = 0; c < columns; c++) {
|
|
const uint8_t character = ram_[(line_data_pointer_[0] + c) & 0xffff];
|
|
const uint8_t pixels = ram_[(
|
|
(line_data_pointer_[1] << index_bits) +
|
|
(character & ((1 << index_bits) - 1))
|
|
) & 0xffff];
|
|
last_read_ = pixels;
|
|
|
|
switch(bpp) {
|
|
default:
|
|
assert(false);
|
|
break;
|
|
|
|
case 1: {
|
|
// This applies ALTIND0 and ALTIND1.
|
|
const uint16_t *palette = alt_ind_palettes[character >> 6];
|
|
output1bpp(pixels);
|
|
} break;
|
|
|
|
case 2: output2bpp(pixels); break;
|
|
case 4: output4bpp(pixels); break;
|
|
case 8: output8bpp(pixels); break;
|
|
}
|
|
}
|
|
}
|
|
|
|
template <int bpp> void Nick::output_attributed(uint16_t *target, int columns) const {
|
|
static_assert(bpp == 1 || bpp == 2 || bpp == 4 || bpp == 8);
|
|
|
|
for(int c = 0; c < columns; c++) {
|
|
const uint8_t pixels = ram_[(line_data_pointer_[1] + c) & 0xffff];
|
|
const uint8_t attributes = ram_[(line_data_pointer_[0] + c) & 0xffff];
|
|
last_read_ = pixels;
|
|
|
|
const uint16_t palette[2] = {
|
|
palette_[attributes >> 4], palette_[attributes & 0x0f]
|
|
};
|
|
output1bpp(pixels);
|
|
}
|
|
}
|
|
|
|
#undef output1bpp
|
|
#undef output2bpp
|
|
#undef output4bpp
|
|
#undef output8bpp
|