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Begins keyboard sketches and notes.

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Thomas Harte 2021-07-30 18:23:15 -04:00
parent 3514e537ca
commit 3d9f86c584
3 changed files with 145 additions and 0 deletions
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92
Machines/Amiga/Keyboard.cpp Normal file
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//
// Keyboard.cpp
// Clock Signal
//
// Created by Thomas Harte on 29/07/2021.
// Copyright © 2021 Thomas Harte. All rights reserved.
//
#include "Keyboard.hpp"
// Notes to self:
//
//
// Before
// the transmission starts, both KCLK and KDAT are high. The keyboard starts
// the transmission by putting out the first data bit (on KDAT), followed by
// a pulse on KCLK (low then high); then it puts out the second data bit and
// pulses KCLK until all eight data bits have been sent.
//
// When the computer has received the eighth bit, it must pulse KDAT low for
// at least 1 (one) microsecond, as a handshake signal to the keyboard. The
// keyboard must be able to detect pulses greater than or equal
// to 1 microsecond. Software MUST pulse the line low for 85 microseconds to
// ensure compatibility with all keyboard models.
//
//
// If the handshake pulse does not arrive within
// 143 ms of the last clock of the transmission, the keyboard will assume
// that the computer is still waiting for the rest of the transmission and is
// therefore out of sync. The keyboard will then attempt to restore sync by
// going into "resync mode." In this mode, the keyboard clocks out a 1 and
// waits for a handshake pulse. If none arrives within 143 ms, it clocks out
// another 1 and waits again.
//
// The keyboard Hard Resets the Amiga by pulling KCLK low and starting a 500
// millisecond timer. When one or more of the keys is released and 500
// milliseconds have passed, the keyboard will release KCLK.
//
// The usual sequence of events will therefore be: power-up; synchronize;
// transmit "initiate power-up key stream" ($FD); transmit "terminate key
// stream" ($FE).
using namespace Amiga;
uint8_t Keyboard::update(uint8_t input) {
// If a bit transmission is ongoing, continue that, up to and including
// the handshake. If no handshake comes, set a macro state of synchronising.
switch(shift_state_) {
case ShiftState::Shifting:
// The keyboard processor sets the KDAT line about 20 microseconds before it
// pulls KCLK low. KCLK stays low for about 20 microseconds, then goes high
// again. The processor waits another 20 microseconds before changing KDAT.
switch(bit_phase_) {
default: break;
case 0: lines_ = Lines::Clock | (shift_sequence_ & 1); break;
case 20: lines_ = (shift_sequence_ & 1); break;
case 40: lines_ = Lines::Clock | (shift_sequence_ & 1); break;
}
bit_phase_ = (bit_phase_ + 1) % 60;
if(!bit_phase_) {
--bits_remaining_;
shift_sequence_ >>= 1;
if(!bits_remaining_) {
shift_state_ = ShiftState::AwaitingHandshake;
}
}
return lines_;
case ShiftState::AwaitingHandshake:
if(!(input & Lines::Data)) {
shift_state_ = ShiftState::Idle;
}
++bit_phase_;
if(bit_phase_ == 143) {
// shift_state_ = ShiftState::Synchronising;
}
return lines_;
default: break;
}
switch(state_) {
case State::Startup:
bit_phase_ = 0;
shift_sequence_ = 0xff;
shift_state_ = ShiftState::Shifting;
break;
}
return lines_;
}

45
Machines/Amiga/Keyboard.hpp Normal file
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//
// Keyboard.hpp
// Clock Signal
//
// Created by Thomas Harte on 29/07/2021.
// Copyright © 2021 Thomas Harte. All rights reserved.
//
#ifndef Keyboard_hpp
#define Keyboard_hpp
#include <cstdint>
namespace Amiga {
class Keyboard {
public:
enum Lines: uint8_t {
Data = (1 << 0),
Clock = (1 << 1),
};
uint8_t update(uint8_t);
private:
enum class ShiftState {
Shifting,
AwaitingHandshake,
Idle,
} shift_state_ = ShiftState::Idle;
enum class State {
Startup,
} state_ = State::Startup;
int bit_phase_ = 0;
uint32_t shift_sequence_ = 0;
int bits_remaining_ = 0;
uint8_t lines_ = 0;
};
}
#endif /* Keyboard_hpp */

8
OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
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4B9EC0EB26B384080060A31F /* Keyboard.cpp in Sources */,
4B894521201967B4007DE474 /* StaticAnalyser.cpp in Sources */,
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