mirror of
https://github.com/TomHarte/CLK.git
synced 2024-06-25 18:30:07 +00:00
Evict the PIT.
This commit is contained in:
Thomas Harte
parent
d3e90ce006
commit
ee6012f6e9
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@ -8,6 +8,8 @@
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#include "PCCompatible.hpp"
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#include "PIT.hpp"
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#include "../../InstructionSets/x86/Decoder.hpp"
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#include "../../InstructionSets/x86/Flags.hpp"
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#include "../../InstructionSets/x86/Instruction.hpp"
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@ -82,6 +84,10 @@ class PIC {
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return 0;
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}
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template <int vector>
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void raise() {
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}
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private:
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bool single_pic_ = false;
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bool four_byte_vectors_ = false;
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@ -197,199 +203,6 @@ class DMA {
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} channels_[4];
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};
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template <bool is_8254>
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class PIT {
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public:
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template <int channel> uint8_t read() {
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const auto result = channels_[channel].read();
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printf("PIT: read from %d; %02x\n", channel, result);
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return result;
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}
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template <int channel> void write(uint8_t value) {
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printf("PIT: write to %d\n", channel);
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channels_[channel].write(value);
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}
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void set_mode(uint8_t value) {
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const int channel_id = (value >> 6) & 3;
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if(channel_id == 3) {
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read_back_ = is_8254;
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// TODO: decode rest of read-back command.
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return;
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}
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printf("PIT: set mode on %d\n", channel_id);
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Channel &channel = channels_[channel_id];
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switch((value >> 4) & 3) {
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default:
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channel.latch_value();
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return;
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case 1: channel.latch_mode = LatchMode::LowOnly; break;
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case 2: channel.latch_mode = LatchMode::HighOnly; break;
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case 3: channel.latch_mode = LatchMode::LowHigh; break;
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}
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channel.is_bcd = value & 1;
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channel.next_access_high = false;
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const auto operating_mode = (value >> 1) & 7;
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switch(operating_mode) {
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default: channel.mode = OperatingMode(operating_mode); break;
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case 6: channel.mode = OperatingMode::RateGenerator; break;
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case 7: channel.mode = OperatingMode::SquareWaveGenerator; break;
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}
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// Set up operating mode.
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switch(channel.mode) {
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default:
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printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
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break;
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case OperatingMode::InterruptOnTerminalCount:
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channel.output = false;
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channel.awaiting_reload = true;
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break;
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case OperatingMode::RateGenerator:
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channel.output = true;
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channel.awaiting_reload = true;
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break;
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}
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}
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void run_for(Cycles cycles) {
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// TODO: be intelligent enough to take ticks outside the loop when appropriate.
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auto ticks = cycles.as<int>();
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while(ticks--) {
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bool output_changed;
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output_changed = channels_[0].advance(1);
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output_changed |= channels_[1].advance(1);
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output_changed |= channels_[2].advance(1);
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}
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}
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private:
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// Supported only on 8254s.
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bool read_back_ = false;
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enum class LatchMode {
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LowOnly,
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HighOnly,
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LowHigh,
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};
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enum class OperatingMode {
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InterruptOnTerminalCount = 0,
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HardwareRetriggerableOneShot = 1,
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RateGenerator = 2,
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SquareWaveGenerator = 3,
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SoftwareTriggeredStrobe = 4,
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HardwareTriggeredStrobe = 5,
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};
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struct Channel {
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LatchMode latch_mode = LatchMode::LowHigh;
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OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
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bool is_bcd = false;
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bool gated = false;
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bool awaiting_reload = true;
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uint16_t counter = 0;
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uint16_t reload = 0;
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uint16_t latch = 0;
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bool output = false;
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bool next_access_high = false;
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void latch_value() {
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latch = counter;
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}
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bool advance(int ticks) {
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if(gated || awaiting_reload) return false;
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// TODO: BCD mode is completely ignored below. Possibly not too important.
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const bool initial_output = output;
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switch(mode) {
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case OperatingMode::InterruptOnTerminalCount:
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// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
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output |= counter <= ticks;
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counter -= ticks;
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break;
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case OperatingMode::RateGenerator:
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// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
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if(counter <= ticks) {
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counter = reload - ticks + counter;
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} else {
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counter -= ticks;
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}
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output = counter != 1;
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break;
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default:
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// TODO.
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break;
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}
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return output != initial_output;
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}
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void write(uint8_t value) {
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switch(latch_mode) {
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case LatchMode::LowOnly:
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reload = (reload & 0xff00) | value;
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break;
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case LatchMode::HighOnly:
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reload = uint16_t((reload & 0x00ff) | (value << 8));
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break;
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case LatchMode::LowHigh:
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next_access_high ^= true;
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if(next_access_high) {
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reload = (reload & 0xff00) | value;
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return;
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}
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reload = uint16_t((reload & 0x00ff) | (value << 8));
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break;
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}
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awaiting_reload = false;
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switch(mode) {
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case OperatingMode::InterruptOnTerminalCount:
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case OperatingMode::RateGenerator:
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counter = reload;
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break;
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}
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}
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uint8_t read() {
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switch(latch_mode) {
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case LatchMode::LowOnly: return uint8_t(latch);
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case LatchMode::HighOnly: return uint8_t(latch >> 8);
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default:
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case LatchMode::LowHigh:
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next_access_high ^= true;
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return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
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break;
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}
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}
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} channels_[3];
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// TODO:
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//
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// channel 0 is connected to IRQ 0;
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// channel 1 is used for DRAM refresh;
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// channel 2 is gated by a PPI output and feeds into the speaker.
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//
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// RateGenerator: output goes high if gated.
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};
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struct Registers {
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public:
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static constexpr bool is_32bit = false;
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209
Machines/PCCompatible/PIT.hpp
Normal file
209
Machines/PCCompatible/PIT.hpp
Normal file
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@ -0,0 +1,209 @@
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//
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// PIT.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 20/11/2023.
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// Copyright © 2023 Thomas Harte. All rights reserved.
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//
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#ifndef PIT_hpp
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#define PIT_hpp
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namespace PCCompatible {
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template <bool is_8254>
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class PIT {
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public:
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template <int channel> uint8_t read() {
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const auto result = channels_[channel].read();
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printf("PIT: read from %d; %02x\n", channel, result);
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return result;
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}
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template <int channel> void write(uint8_t value) {
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printf("PIT: write to %d\n", channel);
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channels_[channel].write(value);
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}
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void set_mode(uint8_t value) {
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const int channel_id = (value >> 6) & 3;
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if(channel_id == 3) {
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read_back_ = is_8254;
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// TODO: decode rest of read-back command.
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return;
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}
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printf("PIT: set mode on %d\n", channel_id);
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Channel &channel = channels_[channel_id];
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switch((value >> 4) & 3) {
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default:
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channel.latch_value();
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return;
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case 1: channel.latch_mode = LatchMode::LowOnly; break;
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case 2: channel.latch_mode = LatchMode::HighOnly; break;
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case 3: channel.latch_mode = LatchMode::LowHigh; break;
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}
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channel.is_bcd = value & 1;
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channel.next_access_high = false;
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const auto operating_mode = (value >> 1) & 7;
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switch(operating_mode) {
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default: channel.mode = OperatingMode(operating_mode); break;
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case 6: channel.mode = OperatingMode::RateGenerator; break;
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case 7: channel.mode = OperatingMode::SquareWaveGenerator; break;
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}
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// Set up operating mode.
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switch(channel.mode) {
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default:
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printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
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break;
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case OperatingMode::InterruptOnTerminalCount:
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channel.output = false;
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channel.awaiting_reload = true;
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break;
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case OperatingMode::RateGenerator:
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channel.output = true;
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channel.awaiting_reload = true;
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break;
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}
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}
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void run_for(Cycles cycles) {
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// TODO: be intelligent enough to take ticks outside the loop when appropriate.
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auto ticks = cycles.as<int>();
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while(ticks--) {
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bool output_changed;
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output_changed = channels_[0].advance(1);
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output_changed |= channels_[1].advance(1);
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output_changed |= channels_[2].advance(1);
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}
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}
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private:
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// Supported only on 8254s.
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bool read_back_ = false;
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enum class LatchMode {
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LowOnly,
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HighOnly,
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LowHigh,
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};
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enum class OperatingMode {
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InterruptOnTerminalCount = 0,
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HardwareRetriggerableOneShot = 1,
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RateGenerator = 2,
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SquareWaveGenerator = 3,
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SoftwareTriggeredStrobe = 4,
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HardwareTriggeredStrobe = 5,
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};
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struct Channel {
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LatchMode latch_mode = LatchMode::LowHigh;
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OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
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bool is_bcd = false;
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bool gated = false;
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bool awaiting_reload = true;
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uint16_t counter = 0;
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uint16_t reload = 0;
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uint16_t latch = 0;
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bool output = false;
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bool next_access_high = false;
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void latch_value() {
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latch = counter;
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}
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bool advance(int ticks) {
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if(gated || awaiting_reload) return false;
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// TODO: BCD mode is completely ignored below. Possibly not too important.
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const bool initial_output = output;
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switch(mode) {
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case OperatingMode::InterruptOnTerminalCount:
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// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
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output |= counter <= ticks;
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counter -= ticks;
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break;
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case OperatingMode::RateGenerator:
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// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
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if(counter <= ticks) {
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counter = reload - ticks + counter;
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} else {
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counter -= ticks;
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}
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output = counter != 1;
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break;
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default:
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// TODO.
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break;
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}
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return output != initial_output;
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}
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void write(uint8_t value) {
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switch(latch_mode) {
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case LatchMode::LowOnly:
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reload = (reload & 0xff00) | value;
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break;
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case LatchMode::HighOnly:
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reload = uint16_t((reload & 0x00ff) | (value << 8));
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break;
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case LatchMode::LowHigh:
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next_access_high ^= true;
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if(next_access_high) {
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reload = (reload & 0xff00) | value;
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return;
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}
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reload = uint16_t((reload & 0x00ff) | (value << 8));
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break;
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}
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awaiting_reload = false;
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switch(mode) {
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case OperatingMode::InterruptOnTerminalCount:
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case OperatingMode::RateGenerator:
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counter = reload;
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break;
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}
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}
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uint8_t read() {
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switch(latch_mode) {
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case LatchMode::LowOnly: return uint8_t(latch);
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case LatchMode::HighOnly: return uint8_t(latch >> 8);
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default:
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case LatchMode::LowHigh:
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next_access_high ^= true;
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return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
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break;
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}
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}
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} channels_[3];
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// TODO:
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//
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// channel 0 is connected to IRQ 0;
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// channel 1 is used for DRAM refresh;
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// channel 2 is gated by a PPI output and feeds into the speaker.
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//
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// RateGenerator: output goes high if gated.
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};
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}
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#endif /* PIT_hpp */
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@ -1142,6 +1142,7 @@
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425739302AFBE47700B7D1E4 /* InOut.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = InOut.hpp; sourceTree = "<group>"; };
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425739362B051EA800B7D1E4 /* PCCompatible.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = PCCompatible.hpp; sourceTree = "<group>"; };
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425739372B051EA800B7D1E4 /* PCCompatible.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PCCompatible.cpp; sourceTree = "<group>"; };
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4267A9C72B0C26FA008A59BB /* PIT.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = PIT.hpp; sourceTree = "<group>"; };
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4281572E2AA0334300E16AA1 /* Carry.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Carry.hpp; sourceTree = "<group>"; };
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428168372A16C25C008ECD27 /* LineLayout.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = LineLayout.hpp; sourceTree = "<group>"; };
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428168392A37AFB4008ECD27 /* DispatcherTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = DispatcherTests.mm; sourceTree = "<group>"; };
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@ -2360,8 +2361,9 @@
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425739352B051EA800B7D1E4 /* PCCompatible */ = {
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isa = PBXGroup;
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children = (
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425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
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425739372B051EA800B7D1E4 /* PCCompatible.cpp */,
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425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
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4267A9C72B0C26FA008A59BB /* PIT.hpp */,
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);
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path = PCCompatible;
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sourceTree = "<group>";
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|
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