6502/CLK
1
0
Fork 0
mirror of https://github.com/TomHarte/CLK.git synced 2025-01-22 19:31:27 +00:00
Code Issues Projects Releases Wiki Activity

Evict the PIT.

Browse Source
This commit is contained in:
Thomas Harte 2023-11-20 19:00:16 -05:00
parent d3e90ce006
commit ee6012f6e9
3 changed files with 218 additions and 194 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

199
Machines/PCCompatible/PCCompatible.cpp
View File

@ -8,6 +8,8 @@
#include "PCCompatible.hpp" #include "PCCompatible.hpp"
#include "PIT.hpp"
#include "../../InstructionSets/x86/Decoder.hpp" #include "../../InstructionSets/x86/Decoder.hpp"
#include "../../InstructionSets/x86/Flags.hpp" #include "../../InstructionSets/x86/Flags.hpp"
#include "../../InstructionSets/x86/Instruction.hpp" #include "../../InstructionSets/x86/Instruction.hpp"
@ -82,6 +84,10 @@ class PIC {
return 0; return 0;
} }
template <int vector>
void raise() {
}
private: private:
bool single_pic_ = false; bool single_pic_ = false;
bool four_byte_vectors_ = false; bool four_byte_vectors_ = false;
@ -197,199 +203,6 @@ class DMA {
} channels_[4]; } channels_[4];
}; };
template <bool is_8254>
class PIT {
public:
template <int channel> uint8_t read() {
const auto result = channels_[channel].read();
printf("PIT: read from %d; %02x\n", channel, result);
return result;
}
template <int channel> void write(uint8_t value) {
printf("PIT: write to %d\n", channel);
channels_[channel].write(value);
}
void set_mode(uint8_t value) {
const int channel_id = (value >> 6) & 3;
if(channel_id == 3) {
read_back_ = is_8254;
// TODO: decode rest of read-back command.
return;
}
printf("PIT: set mode on %d\n", channel_id);
Channel &channel = channels_[channel_id];
switch((value >> 4) & 3) {
default:
channel.latch_value();
return;
case 1: channel.latch_mode = LatchMode::LowOnly; break;
case 2: channel.latch_mode = LatchMode::HighOnly; break;
case 3: channel.latch_mode = LatchMode::LowHigh; break;
}
channel.is_bcd = value & 1;
channel.next_access_high = false;
const auto operating_mode = (value >> 1) & 7;
switch(operating_mode) {
default: channel.mode = OperatingMode(operating_mode); break;
case 6: channel.mode = OperatingMode::RateGenerator; break;
case 7: channel.mode = OperatingMode::SquareWaveGenerator; break;
}
// Set up operating mode.
switch(channel.mode) {
default:
printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
break;
case OperatingMode::InterruptOnTerminalCount:
channel.output = false;
channel.awaiting_reload = true;
break;
case OperatingMode::RateGenerator:
channel.output = true;
channel.awaiting_reload = true;
break;
}
}
void run_for(Cycles cycles) {
// TODO: be intelligent enough to take ticks outside the loop when appropriate.
auto ticks = cycles.as<int>();
while(ticks--) {
bool output_changed;
output_changed = channels_[0].advance(1);
output_changed |= channels_[1].advance(1);
output_changed |= channels_[2].advance(1);
}
}
private:
// Supported only on 8254s.
bool read_back_ = false;
enum class LatchMode {
LowOnly,
HighOnly,
LowHigh,
};
enum class OperatingMode {
InterruptOnTerminalCount = 0,
HardwareRetriggerableOneShot = 1,
RateGenerator = 2,
SquareWaveGenerator = 3,
SoftwareTriggeredStrobe = 4,
HardwareTriggeredStrobe = 5,
};
struct Channel {
LatchMode latch_mode = LatchMode::LowHigh;
OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
bool is_bcd = false;
bool gated = false;
bool awaiting_reload = true;
uint16_t counter = 0;
uint16_t reload = 0;
uint16_t latch = 0;
bool output = false;
bool next_access_high = false;
void latch_value() {
latch = counter;
}
bool advance(int ticks) {
if(gated || awaiting_reload) return false;
// TODO: BCD mode is completely ignored below. Possibly not too important.
const bool initial_output = output;
switch(mode) {
case OperatingMode::InterruptOnTerminalCount:
// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
output |= counter <= ticks;
counter -= ticks;
break;
case OperatingMode::RateGenerator:
// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
if(counter <= ticks) {
counter = reload - ticks + counter;
} else {
counter -= ticks;
}
output = counter != 1;
break;
default:
// TODO.
break;
}
return output != initial_output;
}
void write(uint8_t value) {
switch(latch_mode) {
case LatchMode::LowOnly:
reload = (reload & 0xff00) | value;
break;
case LatchMode::HighOnly:
reload = uint16_t((reload & 0x00ff) | (value << 8));
break;
case LatchMode::LowHigh:
next_access_high ^= true;
if(next_access_high) {
reload = (reload & 0xff00) | value;
return;
}
reload = uint16_t((reload & 0x00ff) | (value << 8));
break;
}
awaiting_reload = false;
switch(mode) {
case OperatingMode::InterruptOnTerminalCount:
case OperatingMode::RateGenerator:
counter = reload;
break;
}
}
uint8_t read() {
switch(latch_mode) {
case LatchMode::LowOnly: return uint8_t(latch);
case LatchMode::HighOnly: return uint8_t(latch >> 8);
default:
case LatchMode::LowHigh:
next_access_high ^= true;
return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
break;
}
}
} channels_[3];
// TODO:
//
// channel 0 is connected to IRQ 0;
// channel 1 is used for DRAM refresh;
// channel 2 is gated by a PPI output and feeds into the speaker.
//
// RateGenerator: output goes high if gated.
};
struct Registers { struct Registers {
public: public:
static constexpr bool is_32bit = false; static constexpr bool is_32bit = false;

209
Machines/PCCompatible/PIT.hpp Normal file
View File

@ -0,0 +1,209 @@
//
// PIT.hpp
// Clock Signal
//
// Created by Thomas Harte on 20/11/2023.
// Copyright © 2023 Thomas Harte. All rights reserved.
//
#ifndef PIT_hpp
#define PIT_hpp
namespace PCCompatible {
template <bool is_8254>
class PIT {
public:
template <int channel> uint8_t read() {
const auto result = channels_[channel].read();
printf("PIT: read from %d; %02x\n", channel, result);
return result;
}
template <int channel> void write(uint8_t value) {
printf("PIT: write to %d\n", channel);
channels_[channel].write(value);
}
void set_mode(uint8_t value) {
const int channel_id = (value >> 6) & 3;
if(channel_id == 3) {
read_back_ = is_8254;
// TODO: decode rest of read-back command.
return;
}
printf("PIT: set mode on %d\n", channel_id);
Channel &channel = channels_[channel_id];
switch((value >> 4) & 3) {
default:
channel.latch_value();
return;
case 1: channel.latch_mode = LatchMode::LowOnly; break;
case 2: channel.latch_mode = LatchMode::HighOnly; break;
case 3: channel.latch_mode = LatchMode::LowHigh; break;
}
channel.is_bcd = value & 1;
channel.next_access_high = false;
const auto operating_mode = (value >> 1) & 7;
switch(operating_mode) {
default: channel.mode = OperatingMode(operating_mode); break;
case 6: channel.mode = OperatingMode::RateGenerator; break;
case 7: channel.mode = OperatingMode::SquareWaveGenerator; break;
}
// Set up operating mode.
switch(channel.mode) {
default:
printf("PIT: %d switches to unimplemented mode %d\n", channel_id, int(channel.mode));
break;
case OperatingMode::InterruptOnTerminalCount:
channel.output = false;
channel.awaiting_reload = true;
break;
case OperatingMode::RateGenerator:
channel.output = true;
channel.awaiting_reload = true;
break;
}
}
void run_for(Cycles cycles) {
// TODO: be intelligent enough to take ticks outside the loop when appropriate.
auto ticks = cycles.as<int>();
while(ticks--) {
bool output_changed;
output_changed = channels_[0].advance(1);
output_changed |= channels_[1].advance(1);
output_changed |= channels_[2].advance(1);
}
}
private:
// Supported only on 8254s.
bool read_back_ = false;
enum class LatchMode {
LowOnly,
HighOnly,
LowHigh,
};
enum class OperatingMode {
InterruptOnTerminalCount = 0,
HardwareRetriggerableOneShot = 1,
RateGenerator = 2,
SquareWaveGenerator = 3,
SoftwareTriggeredStrobe = 4,
HardwareTriggeredStrobe = 5,
};
struct Channel {
LatchMode latch_mode = LatchMode::LowHigh;
OperatingMode mode = OperatingMode::InterruptOnTerminalCount;
bool is_bcd = false;
bool gated = false;
bool awaiting_reload = true;
uint16_t counter = 0;
uint16_t reload = 0;
uint16_t latch = 0;
bool output = false;
bool next_access_high = false;
void latch_value() {
latch = counter;
}
bool advance(int ticks) {
if(gated || awaiting_reload) return false;
// TODO: BCD mode is completely ignored below. Possibly not too important.
const bool initial_output = output;
switch(mode) {
case OperatingMode::InterruptOnTerminalCount:
// Output goes permanently high upon a tick from 1 to 0; reload value is not used on wraparound.
output |= counter <= ticks;
counter -= ticks;
break;
case OperatingMode::RateGenerator:
// Output goes low upon a tick from 2 to 1. It goes high again on 1 to 0, and the reload value is used.
if(counter <= ticks) {
counter = reload - ticks + counter;
} else {
counter -= ticks;
}
output = counter != 1;
break;
default:
// TODO.
break;
}
return output != initial_output;
}
void write(uint8_t value) {
switch(latch_mode) {
case LatchMode::LowOnly:
reload = (reload & 0xff00) | value;
break;
case LatchMode::HighOnly:
reload = uint16_t((reload & 0x00ff) | (value << 8));
break;
case LatchMode::LowHigh:
next_access_high ^= true;
if(next_access_high) {
reload = (reload & 0xff00) | value;
return;
}
reload = uint16_t((reload & 0x00ff) | (value << 8));
break;
}
awaiting_reload = false;
switch(mode) {
case OperatingMode::InterruptOnTerminalCount:
case OperatingMode::RateGenerator:
counter = reload;
break;
}
}
uint8_t read() {
switch(latch_mode) {
case LatchMode::LowOnly: return uint8_t(latch);
case LatchMode::HighOnly: return uint8_t(latch >> 8);
default:
case LatchMode::LowHigh:
next_access_high ^= true;
return next_access_high ? uint8_t(latch) : uint8_t(latch >> 8);
break;
}
}
} channels_[3];
// TODO:
//
// channel 0 is connected to IRQ 0;
// channel 1 is used for DRAM refresh;
// channel 2 is gated by a PPI output and feeds into the speaker.
//
// RateGenerator: output goes high if gated.
};
}
#endif /* PIT_hpp */

4
OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
View File

@ -1142,6 +1142,7 @@
425739302AFBE47700B7D1E4 /* InOut.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = InOut.hpp; sourceTree = "<group>"; }; 425739302AFBE47700B7D1E4 /* InOut.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = InOut.hpp; sourceTree = "<group>"; };
425739362B051EA800B7D1E4 /* PCCompatible.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = PCCompatible.hpp; sourceTree = "<group>"; }; 425739362B051EA800B7D1E4 /* PCCompatible.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = PCCompatible.hpp; sourceTree = "<group>"; };
425739372B051EA800B7D1E4 /* PCCompatible.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PCCompatible.cpp; sourceTree = "<group>"; }; 425739372B051EA800B7D1E4 /* PCCompatible.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = PCCompatible.cpp; sourceTree = "<group>"; };
4267A9C72B0C26FA008A59BB /* PIT.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = PIT.hpp; sourceTree = "<group>"; };
4281572E2AA0334300E16AA1 /* Carry.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Carry.hpp; sourceTree = "<group>"; }; 4281572E2AA0334300E16AA1 /* Carry.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Carry.hpp; sourceTree = "<group>"; };
428168372A16C25C008ECD27 /* LineLayout.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = LineLayout.hpp; sourceTree = "<group>"; }; 428168372A16C25C008ECD27 /* LineLayout.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = LineLayout.hpp; sourceTree = "<group>"; };
428168392A37AFB4008ECD27 /* DispatcherTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = DispatcherTests.mm; sourceTree = "<group>"; }; 428168392A37AFB4008ECD27 /* DispatcherTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = DispatcherTests.mm; sourceTree = "<group>"; };
@ -2360,8 +2361,9 @@
425739352B051EA800B7D1E4 /* PCCompatible */ = { 425739352B051EA800B7D1E4 /* PCCompatible */ = {
isa = PBXGroup; isa = PBXGroup;
children = ( children = (
425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
425739372B051EA800B7D1E4 /* PCCompatible.cpp */, 425739372B051EA800B7D1E4 /* PCCompatible.cpp */,
425739362B051EA800B7D1E4 /* PCCompatible.hpp */,
4267A9C72B0C26FA008A59BB /* PIT.hpp */,
); );
path = PCCompatible; path = PCCompatible;
sourceTree = "<group>"; sourceTree = "<group>";