mirror of https://github.com/sethm/symon.git
161 lines
4.1 KiB
Java
161 lines
4.1 KiB
Java
/*
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* Copyright (c) 2008-2014 Seth J. Morabito <web@loomcom.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package com.loomcom.symon.devices;
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import com.loomcom.symon.exceptions.MemoryRangeException;
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/**
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* Abstract base class for ACIAS such as the 6551 and 6580
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*/
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public abstract class Acia extends Device {
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private String name;
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/**
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* Register addresses
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*/
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int baseAddress;
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boolean receiveIrqEnabled = false;
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boolean transmitIrqEnabled = false;
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boolean overrun = false;
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long lastTxWrite = 0;
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long lastRxRead = 0;
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int baudRate = 0;
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long baudRateDelay = 0;
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/**
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* Read/Write buffers
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*/
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int rxChar = 0;
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int txChar = 0;
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boolean rxFull = false;
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boolean txEmpty = true;
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public Acia(int address, int size, String name) throws MemoryRangeException {
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super(address, address + size - 1, name);
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this.name = name;
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this.baseAddress = address;
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}
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/*
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* Calculate the delay in nanoseconds between successive read/write operations, based on the
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* configured baud rate.
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*/
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private long calculateBaudRateDelay() {
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if (baudRate > 0) {
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// TODO: This is a pretty rough approximation based on 8 bits per character,
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// and 1/baudRate per bit. It could certainly be improved
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return (long)((1.0 / baudRate) * 1000000000 * 8);
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} else {
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return 0;
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}
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}
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/**
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* @return The simulated baud rate in bps.
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*/
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public int getBaudRate() {
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return baudRate;
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}
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/**
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* Set the baud rate of the simulated ACIA.
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*
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* @param rate The baud rate in bps. 0 means no simulated baud rate delay.
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*/
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public void setBaudRate(int rate) {
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this.baudRate = rate;
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this.baudRateDelay = calculateBaudRateDelay();
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}
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/**
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* @return The contents of the status register.
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*/
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public abstract int statusReg();
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@Override
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public String toString() {
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return name + "@" + String.format("%04X", baseAddress);
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}
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public synchronized int rxRead() {
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lastRxRead = System.nanoTime();
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overrun = false;
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rxFull = false;
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return rxChar;
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}
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public synchronized void rxWrite(int data) {
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if(rxFull) {
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overrun = true;
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}
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rxFull = true;
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if (receiveIrqEnabled) {
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getBus().assertIrq();
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}
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rxChar = data;
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}
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public synchronized int txRead() {
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txEmpty = true;
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if (transmitIrqEnabled) {
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getBus().assertIrq();
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}
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return txChar;
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}
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public synchronized void txWrite(int data) {
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lastTxWrite = System.nanoTime();
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txChar = data;
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txEmpty = false;
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}
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/**
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* @return true if there is character data in the TX register.
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*/
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public boolean hasTxChar() {
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return !txEmpty;
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}
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/**
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* @return true if there is character data in the RX register.
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*/
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public boolean hasRxChar() {
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return rxFull;
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}
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}
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