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PIT output now reaches the PIC.
This commit is contained in:
Thomas Harte
parent
f0e2ef5e28
commit
695282b838
@ -84,8 +84,13 @@ 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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template <int input>
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void apply_edge(bool final_level) {
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const uint8_t input_mask = 1 << input;
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if(mask_ & input_mask) {
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return;
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}
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printf("PIC: Unmasked input %d switches to level %d\n", input, final_level);
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}
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private:
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@ -103,6 +108,30 @@ class PIC {
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} config_;
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};
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class PITObserver {
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public:
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PITObserver(PIC &pic) : pic_(pic) {}
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template <int channel>
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void update_output(bool new_level) {
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switch(channel) {
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default: break;
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case 0: pic_.apply_edge<0>(new_level); break;
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}
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}
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private:
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PIC &pic_;
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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 (presumably connected to DMA?);
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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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using PIT = i8237<false, PITObserver>;
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class i8255PortHandler : public Intel::i8255::PortHandler {
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// Likely to be helpful: https://github.com/tmk/tmk_keyboard/wiki/IBM-PC-XT-Keyboard-Protocol
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public:
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@ -452,7 +481,7 @@ struct Memory {
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class IO {
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public:
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IO(PIT<false> &pit, DMA &dma, PPI &ppi, PIC &pic) : pit_(pit), dma_(dma), ppi_(ppi), pic_(pic) {}
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IO(PIT &pit, DMA &dma, PPI &ppi, PIC &pic) : pit_(pit), dma_(dma), ppi_(ppi), pic_(pic) {}
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template <typename IntT> void out(uint16_t port, IntT value) {
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switch(port) {
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@ -555,7 +584,7 @@ class IO {
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}
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private:
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PIT<false> &pit_;
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PIT &pit_;
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DMA &dma_;
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PPI &ppi_;
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PIC &pic_;
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@ -610,7 +639,7 @@ class ConcreteMachine:
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ConcreteMachine(
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[[maybe_unused]] const Analyser::Static::Target &target,
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const ROMMachine::ROMFetcher &rom_fetcher
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) : ppi_(ppi_handler_), context(pit_, dma_, ppi_, pic_) {
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) : pit_observer_(pic_), pit_(pit_observer_), ppi_(ppi_handler_), context(pit_, dma_, ppi_, pic_) {
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// Use clock rate as a MIPS count; keeping it as a multiple or divisor of the PIT frequency is easy.
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static constexpr int pit_frequency = 1'193'182;
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set_clock_rate(double(pit_frequency) * double(PitMultiplier) / double(PitDivisor)); // i.e. almost 0.4 MIPS for an XT.
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@ -668,14 +697,17 @@ class ConcreteMachine:
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}
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private:
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PIT<false> pit_;
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DMA dma_;
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i8255PortHandler ppi_handler_;
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PPI ppi_;
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PIC pic_;
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DMA dma_;
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PITObserver pit_observer_;
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i8255PortHandler ppi_handler_;
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PIT pit_;
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PPI ppi_;
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struct Context {
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Context(PIT<false> &pit, DMA &dma, PPI &ppi, PIC &pic) :
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Context(PIT &pit, DMA &dma, PPI &ppi, PIC &pic) :
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segments(registers),
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memory(registers, segments),
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flow_controller(registers, segments),
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@ -11,15 +11,17 @@
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namespace PCCompatible {
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template <bool is_8254>
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class PIT {
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template <bool is_8254, typename PITObserver>
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class i8237 {
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public:
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i8237(PITObserver &observer) : observer_(observer) {}
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template <int channel> uint8_t read() {
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return channels_[channel].read();
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}
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template <int channel> void write(uint8_t value) {
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channels_[channel].write(value);
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channels_[channel].template write<channel>(observer_, value);
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}
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void set_mode(uint8_t value) {
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@ -29,20 +31,27 @@ class PIT {
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read_back_ = is_8254;
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return;
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}
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channels_[channel_id].set_mode(value);
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switch(channel_id) {
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case 0: channels_[0].template set_mode<0>(observer_, value); break;
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case 1: channels_[1].template set_mode<1>(observer_, value); break;
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case 2: channels_[2].template set_mode<2>(observer_, value); 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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channels_[0].advance(1);
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channels_[1].advance(1);
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channels_[2].advance(1);
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channels_[0].template advance<0>(observer_, 1);
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channels_[1].template advance<1>(observer_, 1);
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channels_[2].template advance<2>(observer_, 1);
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}
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}
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private:
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// The target for output changes.
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PITObserver &observer_;
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// Supported only on 8254s.
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bool read_back_ = false;
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@ -80,7 +89,8 @@ class PIT {
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latch = counter;
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}
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void set_mode(uint8_t value) {
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template <int channel>
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void set_mode(PITObserver &observer, uint8_t value) {
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switch((value >> 4) & 3) {
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default:
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latch_value();
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@ -108,19 +118,20 @@ class PIT {
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case OperatingMode::InterruptOnTerminalCount:
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case OperatingMode::HardwareRetriggerableOneShot:
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set_output(false);
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set_output<channel>(observer, false);
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awaiting_reload = true;
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break;
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case OperatingMode::RateGenerator:
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case OperatingMode::SquareWaveGenerator:
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set_output(true);
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set_output<channel>(observer, true);
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awaiting_reload = true;
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break;
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}
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}
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void advance(int ticks) {
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template <int channel>
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void advance(PITObserver &observer, int ticks) {
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if(gated || awaiting_reload) return;
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// TODO: BCD mode is completely ignored below. Possibly not too important.
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@ -128,7 +139,7 @@ class PIT {
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case OperatingMode::InterruptOnTerminalCount:
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case OperatingMode::HardwareRetriggerableOneShot:
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// Output goes permanently high upon a tick from 1 to 0; reload value is not reused.
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set_output(output | (counter <= ticks));
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set_output<channel>(observer, output | (counter <= ticks));
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counter -= ticks;
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break;
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@ -138,7 +149,7 @@ class PIT {
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// If there's a step from 1 to 0 within the next batch of ticks,
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// toggle output and apply a reload.
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if(counter && ticks >= counter) {
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set_output(output ^ true);
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set_output<channel>(observer, output ^ true);
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ticks -= counter;
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const uint16_t reload_mask = output ? 0xffff : 0xfffe;
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@ -155,7 +166,7 @@ class PIT {
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// Check for a step from 2 to 1 within the next batch of ticks, which would cause output
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// to go high.
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if(counter > 1 && ticks >= counter - 1) {
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set_output(true);
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set_output<channel>(observer, true);
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ticks -= counter - 1;
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counter = 1;
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continue;
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@ -163,7 +174,7 @@ class PIT {
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// If there is a step from 1 to 0, reload and set output back to low.
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if(counter && ticks >= counter) {
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set_output(false);
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set_output<channel>(observer, false);
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ticks -= counter;
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counter = reload;
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continue;
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@ -180,7 +191,8 @@ class PIT {
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}
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}
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void write(uint8_t value) {
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template <int channel>
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void write([[maybe_unused]] PITObserver &observer, 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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@ -225,22 +237,20 @@ class PIT {
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}
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}
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void set_output(bool level) {
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template <int channel>
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void set_output(PITObserver &observer, bool level) {
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if(output == level) {
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return;
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}
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// TODO: how should time be notified?
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observer.template update_output<channel>(level);
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output = level;
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// TODO: notify _someone_.
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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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