PIC8259.h

/*
  Created by Fabrizio Di Vittorio (fdivitto2013@gmail.com) - <http://www.fabgl.com>
  Copyright (c) 2019-2022 Fabrizio Di Vittorio.
  All rights reserved.
 
 
* Please contact fdivitto2013@gmail.com if you need a commercial license.
 
 
* This library and related software is available under GPL v3.
 
  FabGL is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
 
  FabGL is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with FabGL.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 
#pragma once
 
#include "fabgl.h"
 
 
 
namespace fabgl {
 
 
// PIC 8259 (Programmable Interrupt Controller)
 
// Limitations:
//   - only 8086 mode
//   - only single mode
//   - don't care about input level or edge
//   - don't care about buffered mode or unbuffered mode
//   - don't support special fully nested mode
//   - priority is fixed to IR0 = highest
//   - don't support Poll command
//   - don't support Special Mask
 
 
 
class PIC8259 {
 
public:
 
  void reset();
 
  void write(int addr, uint8_t value);
  uint8_t read(int addr);
 
  // Device->8259: a device reports interrupt to 8259
  bool signalInterrupt(int intnum);
 
  // 8259->CPU: 8259 reports interrupt to CPU
  bool pendingInterrupt()                               { return m_pendingInterrupt; }
 
  // 8259->CPU: 8259 reports interrupt number to CPU
  int pendingInterruptNum()                             { return m_baseVector | m_pendingIR; }
 
  // CPU->8259: CPU acks the pending interrupt to 8259
  void ackPendingInterrupt();
 
 
private:
 
  void performEOI();
  int getHighestPriorityBitNum(uint8_t value);
  void setPendingInterrupt();
 
  uint8_t m_state; // all zeros = ready, bit 0 = waiting for ICW2, bit 1 = waiting for ICW3, bit 2 = waiting for ICW4
 
  uint8_t m_baseVector; // bits 3..7 got from ICW2
  bool    m_autoEOI;
 
  uint8_t m_IRR;  // Interrupt Request Register
  uint8_t m_ISR;  // In-Service Register
  uint8_t m_IMR;  // Interrupt Mask Register
 
  // if true port 0 reads ISR, otherwise port 0 reads IRR
  bool    m_readISR;
 
  bool    m_pendingInterrupt;
  uint8_t m_pendingIR;
 
};
 
 
} // namespace fabgl