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289 lines
6.2 KiB
C++
289 lines
6.2 KiB
C++
//
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// YamahaCommands.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 26/01/2023.
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// Copyright © 2023 Thomas Harte. All rights reserved.
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//
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#ifndef YamahaCommands_hpp
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#define YamahaCommands_hpp
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#include "AccessEnums.hpp"
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namespace TI {
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namespace TMS {
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// MARK: - Generics.
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struct Vector {
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int v[2]{};
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template <int offset, bool high> void set(uint8_t value) {
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constexpr uint8_t mask = high ? (offset ? 0x3 : 0x1) : 0xff;
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constexpr int shift = high ? 8 : 0;
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v[offset] = (v[offset] & ~(mask << shift)) | (value << shift);
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}
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template <int offset> void add(int amount) {
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v[offset] += amount;
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if constexpr (offset == 1) {
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v[offset] &= 0x3ff;
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} else {
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v[offset] &= 0x1ff;
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}
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}
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Vector & operator += (const Vector &rhs) {
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add<0>(rhs.v[0]);
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add<1>(rhs.v[1]);
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return *this;
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}
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};
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struct CommandContext {
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Vector source;
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Vector destination;
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Vector size;
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uint8_t arguments = 0;
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/// Colour as written by the CPU.
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uint8_t colour = 0;
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/// The low four bits of the CPU-written colour, repeated twice.
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uint8_t colour4bpp = 0;
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/// The low two bits of the CPU-written colour, repeated four times.
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uint8_t colour2bpp = 0;
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enum class LogicalOperation {
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Copy = 0b0000,
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And = 0b0001,
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Or = 0b0010,
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Xor = 0b0011,
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Not = 0b0100,
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};
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LogicalOperation pixel_operation;
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bool test_source;
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};
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struct Command {
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// In net:
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//
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// This command is blocked until @c access has been performed, reading
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// from or writing to @c value. It should not be performed until at least
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// @c cycles have passed.
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enum class AccessType {
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/// Plots a single pixel of the current contextual colour at @c location,
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/// which occurs as a read, then a 24-cycle pause, then a write.
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PlotPoint,
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/// Blocks until the next CPU write to the colour register.
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WaitForColourReceipt,
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/// Writes an entire byte to the location containing the current @c location.
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WriteByte,
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};
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AccessType access = AccessType::PlotPoint;
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int cycles = 0;
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bool is_cpu_transfer = false;
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Vector location;
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/// Current command parameters.
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CommandContext &context;
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Command(CommandContext &context) : context(context) {}
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/// @returns @c true if all output from this command is done; @c false otherwise.
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virtual bool done() = 0;
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/// Repopulates the fields above with the next action to take, being provided with the
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/// number of pixels per byte in the current screen mode.
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virtual void advance(int pixels_per_byte) = 0;
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protected:
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template <int axis> void advance_axis(int offset = 1) {
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context.destination.add<axis>(context.arguments & (0x4 << axis) ? -offset : offset);
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}
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};
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// MARK: - Line drawing.
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namespace Commands {
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/// Implements the LINE command, which is plain-old Bresenham.
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///
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/// Per Grauw timing is:
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///
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/// * 88 cycles between every pixel plot;
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/// * plus an additional 32 cycles if a step along the minor axis is taken.
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struct Line: public Command {
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public:
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Line(CommandContext &context) : Command(context) {
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// context.destination = start position;
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// context.size.v[0] = long side dots;
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// context.size.v[1] = short side dots;
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// context.arguments => direction
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location = context.destination;
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position_ = context.size.v[1];
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numerator_ = position_ << 1;
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denominator_ = context.size.v[0] << 1;
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cycles = 32;
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access = AccessType::PlotPoint;
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}
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bool done() final {
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return !context.size.v[0];
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}
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void advance(int) final {
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--context.size.v[0];
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cycles = 88;
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// b0: 1 => long direction is y;
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// 0 => long direction is x.
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//
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// b2: 1 => x direction is left;
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// 0 => x direction is right.
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//
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// b3: 1 => y direction is up;
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// 0 => y direction is down.
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if(context.arguments & 0x1) {
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advance_axis<1>();
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} else {
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advance_axis<0>();
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}
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position_ -= numerator_;
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if(position_ < 0) {
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position_ += denominator_;
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cycles += 32;
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if(context.arguments & 0x1) {
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advance_axis<0>();
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} else {
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advance_axis<1>();
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}
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}
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}
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private:
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int position_, numerator_, denominator_, duration_;
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};
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/// Implements the PSET command, which plots a single pixel.
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///
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/// No timings are documented, so this'll output as quickly as possible.
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struct PointSet: public Command {
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public:
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PointSet(CommandContext &context) : Command(context) {
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cycles = 0;
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access = AccessType::PlotPoint;
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location = context.destination;
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}
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bool done() final {
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return done_;
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}
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void advance(int) final {
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done_ = true;
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}
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private:
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bool done_ = false;
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};
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struct LogicalMoveFromCPU: public Command {
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public:
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LogicalMoveFromCPU(CommandContext &context) : Command(context) {
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is_cpu_transfer = true;
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start_x_ = context.destination.v[0];
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width_ = context.size.v[0];
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// This command is started with the first colour ready to transfer.
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cycles = 32;
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access = AccessType::PlotPoint;
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location = context.destination;
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}
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void advance(int) final {
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switch(access) {
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default: break;
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case AccessType::WaitForColourReceipt:
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cycles = 32;
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location = context.destination;
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access = AccessType::PlotPoint;
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break;
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case AccessType::PlotPoint:
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cycles = 0;
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access = AccessType::WaitForColourReceipt;
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advance_axis<0>();
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--context.size.v[0];
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if(!context.size.v[0]) {
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cycles = 64;
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context.size.v[0] = width_;
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context.destination.v[0] = start_x_;
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advance_axis<1>();
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--context.size.v[1];
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}
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break;
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}
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}
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bool done() final {
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return !context.size.v[1] || !width_;
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}
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private:
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int start_x_ = 0, width_ = 0;
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};
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struct HighSpeedFill: public Command {
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HighSpeedFill(CommandContext &context) : Command(context) {
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start_x_ = context.destination.v[0];
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width_ = context.size.v[0];
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cycles = 56;
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access = AccessType::WriteByte;
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location = context.destination;
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}
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bool done() final {
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return true;
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}
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void advance(int pixels_per_byte) final {
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cycles = 48;
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// TODO: step at byte speed, not pixel speed.
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advance_axis<0>(pixels_per_byte);
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--context.size.v[0];
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if(!context.size.v[0]) {
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cycles += 56;
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context.size.v[0] = width_;
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context.destination.v[0] = start_x_;
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advance_axis<1>();
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--context.size.v[1];
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}
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location = context.destination;
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}
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private:
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int start_x_ = 0, width_ = 0;
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};
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}
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}
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}
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#endif /* YamahaCommands_hpp */
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