mirror of
https://github.com/TomHarte/CLK.git
synced 2024-08-21 04:29:34 +00:00
168 lines
5.7 KiB
C++
168 lines
5.7 KiB
C++
//
|
|
// BlitterSequencer.hpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 19/08/2022.
|
|
// Copyright © 2022 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#ifndef BlitterSequencer_hpp
|
|
#define BlitterSequencer_hpp
|
|
|
|
#include <array>
|
|
|
|
namespace Amiga {
|
|
|
|
/*!
|
|
Statefully provides the next access the Blitter should make.
|
|
|
|
TODO: determine the actual logic here, rather than
|
|
relying on tables.
|
|
*/
|
|
class BlitterSequencer {
|
|
public:
|
|
enum class Channel {
|
|
/// Tells the caller to calculate and load a new piece of output
|
|
/// into the output pipeline.
|
|
///
|
|
/// If any inputs are enabled then a one-slot output pipeline applies:
|
|
/// output will rest in the pipeline for one write phase before being written.
|
|
Write,
|
|
/// Indicates that a write should occur if anything is in the pipeline, otherwise
|
|
/// no activity should occur.
|
|
FlushPipeline,
|
|
/// The caller should read from channel C.
|
|
C,
|
|
/// The caller should read from channel B.
|
|
B,
|
|
/// The caller should read from channel A.
|
|
A,
|
|
/// Indicates an unused DMA slot.
|
|
None
|
|
};
|
|
|
|
/// Sets the current control value, which indicates which
|
|
/// channels are enabled.
|
|
void set_control(int control) {
|
|
control_ = control & 0xf;
|
|
index_ = 0; // TODO: this probably isn't accurate; case caught is a change
|
|
// of control values during a blit.
|
|
}
|
|
|
|
/// Indicates that blitting should conclude after this step, i.e.
|
|
/// whatever is being fetched now is part of the final set of input data;
|
|
/// this is safe to call following a fetch request on any channel.
|
|
void complete() {
|
|
next_phase_ =
|
|
(control_ == 0x9 || control_ == 0xb || control_ == 0xd) ?
|
|
Phase::PauseAndComplete : Phase::Complete;
|
|
}
|
|
|
|
/// Begins a blit operation.
|
|
void begin() {
|
|
phase_ = next_phase_ = Phase::Ongoing;
|
|
index_ = loop_ = 0;
|
|
}
|
|
|
|
/// Provides the next channel to fetch from, or that a write is required,
|
|
/// along with a count of complete channel iterations so far completed.
|
|
std::pair<Channel, int> next() {
|
|
switch(phase_) {
|
|
default: break;
|
|
|
|
case Phase::Complete:
|
|
return std::make_pair(Channel::FlushPipeline, loop_);
|
|
|
|
case Phase::PauseAndComplete:
|
|
phase_ = Phase::Complete;
|
|
return std::make_pair(Channel::None, loop_);
|
|
}
|
|
|
|
Channel next = Channel::None;
|
|
|
|
switch(control_) {
|
|
default: break;
|
|
|
|
case 0: next = next_channel(pattern0); break;
|
|
case 1: next = next_channel(pattern1); break;
|
|
case 2: next = next_channel(pattern2); break;
|
|
case 3: next = next_channel(pattern3); break;
|
|
case 4: next = next_channel(pattern4); break;
|
|
case 5: next = next_channel(pattern5); break;
|
|
case 6: next = next_channel(pattern6); break;
|
|
case 7: next = next_channel(pattern7); break;
|
|
case 8: next = next_channel(pattern8); break;
|
|
case 9: next = next_channel(pattern9); break;
|
|
case 10: next = next_channel(patternA); break;
|
|
case 11: next = next_channel(patternB); break;
|
|
case 12: next = next_channel(patternC); break;
|
|
case 13: next = next_channel(patternD); break;
|
|
case 14: next = next_channel(patternE); break;
|
|
case 15: next = next_channel(patternF); break;
|
|
}
|
|
|
|
return std::make_pair(next, loop_);
|
|
}
|
|
|
|
template <int channel> bool channel_enabled() {
|
|
return control_ & (8 >> channel);
|
|
}
|
|
|
|
private:
|
|
static constexpr std::array<Channel, 1> pattern0 = { Channel::None };
|
|
static constexpr std::array<Channel, 2> pattern1 = { Channel::Write, Channel::None };
|
|
static constexpr std::array<Channel, 2> pattern2 = { Channel::C, Channel::None };
|
|
static constexpr std::array<Channel, 3> pattern3 = { Channel::C, Channel::Write, Channel::None };
|
|
static constexpr std::array<Channel, 3> pattern4 = { Channel::B, Channel::None, Channel::None };
|
|
static constexpr std::array<Channel, 3> pattern5 = { Channel::B, Channel::Write, Channel::None };
|
|
static constexpr std::array<Channel, 3> pattern6 = { Channel::B, Channel::C, Channel::None };
|
|
static constexpr std::array<Channel, 4> pattern7 = { Channel::B, Channel::C, Channel::Write, Channel::None };
|
|
static constexpr std::array<Channel, 2> pattern8 = { Channel::A, Channel::None };
|
|
static constexpr std::array<Channel, 2> pattern9 = { Channel::A, Channel::Write };
|
|
static constexpr std::array<Channel, 2> patternA = { Channel::A, Channel::C };
|
|
static constexpr std::array<Channel, 3> patternB = { Channel::A, Channel::C, Channel::Write };
|
|
static constexpr std::array<Channel, 3> patternC = { Channel::A, Channel::B, Channel::None };
|
|
static constexpr std::array<Channel, 3> patternD = { Channel::A, Channel::B, Channel::Write };
|
|
static constexpr std::array<Channel, 3> patternE = { Channel::A, Channel::B, Channel::C };
|
|
static constexpr std::array<Channel, 4> patternF = { Channel::A, Channel::B, Channel::C, Channel::Write };
|
|
template <typename ArrayT> Channel next_channel(const ArrayT &list) {
|
|
loop_ += index_ / list.size();
|
|
index_ %= list.size();
|
|
const Channel result = list[index_];
|
|
++index_;
|
|
if(index_ == list.size()) {
|
|
phase_ = next_phase_;
|
|
}
|
|
return result;
|
|
}
|
|
|
|
// Current control flags, i.e. which channels are enabled.
|
|
int control_ = 0;
|
|
|
|
// Index into the pattern table for this blit.
|
|
size_t index_ = 0;
|
|
|
|
// Number of times the entire pattern table has been completed.
|
|
int loop_ = 0;
|
|
|
|
enum class Phase {
|
|
/// Return the next thing in the pattern table and advance.
|
|
/// If looping from the end of the pattern table to the start,
|
|
/// set phase_ to next_phase_.
|
|
Ongoing,
|
|
/// Return a Channel::None and advancce to phase_ = Phase::Complete.
|
|
PauseAndComplete,
|
|
/// Return Channel::Write indefinitely.
|
|
Complete
|
|
};
|
|
|
|
// Current sequencer pahse.
|
|
Phase phase_ = Phase::Complete;
|
|
// Phase to assume at the end of this iteration of the sequence table.
|
|
Phase next_phase_ = Phase::Complete;
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* BlitterSequencer_hpp */
|