1
0
mirror of https://github.com/TomHarte/CLK.git synced 2024-12-12 08:30:05 +00:00
CLK/Components/8272/CommandDecoder.hpp

219 lines
4.9 KiB
C++
Raw Normal View History

//
// CommandDecoder.hpp
// Clock Signal
//
// Created by Thomas Harte on 24/11/2023.
// Copyright © 2023 Thomas Harte. All rights reserved.
//
#pragma once
#include <cstdint>
#include <cstddef>
#include <vector>
namespace Intel::i8272 {
2023-11-28 04:05:37 +00:00
enum class Command {
ReadData = 0x06,
ReadDeletedData = 0x0c,
2023-11-28 04:05:37 +00:00
WriteData = 0x05,
WriteDeletedData = 0x09,
2023-11-28 04:05:37 +00:00
ReadTrack = 0x02,
ReadID = 0x0a,
FormatTrack = 0x0d,
2023-11-28 04:05:37 +00:00
ScanLow = 0x11,
ScanLowOrEqual = 0x19,
ScanHighOrEqual = 0x1d,
2023-11-28 04:05:37 +00:00
Recalibrate = 0x07,
Seek = 0x0f,
2023-11-28 04:05:37 +00:00
SenseInterruptStatus = 0x08,
Specify = 0x03,
SenseDriveStatus = 0x04,
2023-11-28 04:05:37 +00:00
Invalid = 0x00,
};
2023-11-28 04:05:37 +00:00
class CommandDecoder {
public:
/// Add a byte to the current command.
void push_back(uint8_t byte) {
command_.push_back(byte);
}
/// Reset decoding.
void clear() {
command_.clear();
}
/// @returns @c true if an entire command has been received; @c false if further bytes are needed.
bool has_command() const {
if(!command_.size()) {
return false;
}
static constexpr std::size_t required_lengths[32] = {
0, 0, 9, 3, 2, 9, 9, 2,
1, 9, 2, 0, 9, 6, 0, 3,
0, 9, 0, 0, 0, 0, 0, 0,
0, 9, 0, 0, 0, 9, 0, 0,
};
return command_.size() >= required_lengths[command_[0] & 0x1f];
}
/// @returns The command requested. Valid only if @c has_command() is @c true.
Command command() const {
const auto command = Command(command_[0] & 0x1f);
switch(command) {
case Command::ReadData: case Command::ReadDeletedData:
case Command::WriteData: case Command::WriteDeletedData:
case Command::ReadTrack: case Command::ReadID:
case Command::FormatTrack:
case Command::ScanLow: case Command::ScanLowOrEqual:
case Command::ScanHighOrEqual:
case Command::Recalibrate: case Command::Seek:
case Command::SenseInterruptStatus:
case Command::Specify: case Command::SenseDriveStatus:
return command;
default: return Command::Invalid;
}
}
//
// Commands that specify geometry; i.e.
//
// * ReadData;
// * ReadDeletedData;
// * WriteData;
// * WriteDeletedData;
// * ReadTrack;
// * ScanEqual;
// * ScanLowOrEqual;
// * ScanHighOrEqual.
//
/// @returns @c true if this command specifies geometry, in which case geomtry() is well-defined.
/// @c false otherwise.
bool has_geometry() const { return command_.size() == 9; }
struct Geometry {
uint8_t cylinder, head, sector, size, end_of_track;
};
Geometry geometry() const {
Geometry result;
result.cylinder = command_[2];
result.head = command_[3];
result.sector = command_[4];
result.size = command_[5];
result.end_of_track = command_[6];
return result;
}
//
// Commands that imply data access; i.e.
//
// * ReadData;
// * ReadDeletedData;
// * WriteData;
// * WriteDeletedData;
// * ReadTrack;
// * ReadID;
// * FormatTrack;
// * ScanLow;
// * ScanLowOrEqual;
// * ScanHighOrEqual.
//
/// @returns @c true if this command involves reading or writing data, in which case target() will be valid.
/// @c false otherwise.
2023-11-26 20:29:08 +00:00
bool is_access() const {
switch(command()) {
case Command::ReadData: case Command::ReadDeletedData:
case Command::WriteData: case Command::WriteDeletedData:
case Command::ReadTrack: case Command::ReadID:
case Command::FormatTrack:
case Command::ScanLow: case Command::ScanLowOrEqual:
case Command::ScanHighOrEqual:
return true;
default:
return false;
}
}
struct AccessTarget {
uint8_t drive, head;
bool mfm, skip_deleted;
};
AccessTarget target() const {
AccessTarget result;
result.drive = command_[1] & 0x03;
result.head = (command_[1] >> 2) & 0x01;
result.mfm = command_[0] & 0x40;
result.skip_deleted = command_[0] & 0x20;
return result;
}
uint8_t drive_head() const {
return command_[1] & 7;
}
//
// Command::FormatTrack
//
struct FormatSpecs {
uint8_t bytes_per_sector;
uint8_t sectors_per_track;
uint8_t gap3_length;
uint8_t filler;
};
FormatSpecs format_specs() const {
FormatSpecs result;
result.bytes_per_sector = command_[2];
result.sectors_per_track = command_[3];
result.gap3_length = command_[4];
result.filler = command_[5];
return result;
}
//
// Command::Seek
//
/// @returns The desired target track.
uint8_t seek_target() const {
return command_[2];
}
//
// Command::Specify
//
struct SpecifySpecs {
// The below are all in milliseconds.
uint8_t step_rate_time;
uint8_t head_unload_time;
uint8_t head_load_time;
bool use_dma;
};
SpecifySpecs specify_specs() const {
SpecifySpecs result;
result.step_rate_time = 16 - (command_[1] >> 4); // i.e. 1 to 16ms
result.head_unload_time = uint8_t((command_[1] & 0x0f) << 4); // i.e. 16 to 240ms
result.head_load_time = command_[2] & ~1; // i.e. 2 to 254 ms in increments of 2ms
result.use_dma = !(command_[2] & 1);
return result;
}
private:
std::vector<uint8_t> command_;
};
}