src/Eeprom.cpp

   1 /*
   2  *      avr-sim: An atmel AVR simulator
   3  *  Copyright (C) 2008  Tom Haber
   4  *
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation, either version 3 of the License, or
   8  *  (at your option) any later version.
   9
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "Eeprom.h"
  20 #include "Bus.h"
  21 #include "Registers.h"
  22 #include <cstring>
  23
  24 #define EERIE   (1<<3)
  25 #define EEMWE   (1<<2)
  26 #define EEWE    (1<<1)
  27 #define EERE    (1<<0)
  28 #define CLEAR   0xf8
  29
  30 namespace avr {
  31
  32         Eeprom::Eeprom(Bus & bus, unsigned int size, unsigned int rdyVec)
  33                 : Hardware(bus), Memory(size), rdyVec(rdyVec), oldEecr(0) {
  34         }
  35
  36         Eeprom::~Eeprom() {
  37         }
  38
  39         void Eeprom::writeToAddress(unsigned int addr, unsigned char val) {
  40                 write(addr, &val);
  41         }
  42
  43         unsigned char Eeprom::readFromAddress(unsigned int addr) {
  44             return readByte(addr);
  45         }
  46
  47         bool Eeprom::attachReg(const char *name, IORegister *reg) {
  48                 if( strcmp(name, "eecr") == 0 )
  49                         eecr = reg;
  50                 else if( strcmp(name, "eedr") == 0 ) {
  51                         eedr = reg;
  52                         return true;
  53                 } else if( strcmp(name, "eearl") == 0 )
  54                         eearl = reg;
  55                 else if( strcmp(name, "eearh") == 0 )
  56                         eearh = reg;
  57                 else
  58                         return false;
  59
  60                 reg->registerHW(this);
  61                 return true;
  62         }
  63
  64         void Eeprom::regChanged( IORegister *reg ) {
  65                 if( reg == eearh )
  66                     eear = (eear & 0x00ff) | (*eearh << 8);
  67                 else if( reg == eearl )
  68                         eear = (eear & 0xff00) | (*eearl);
  69                 else if( reg == eecr )
  70                         setEECR( *eecr );
  71         }
  72
  73         void Eeprom::step() {
  74                 switch( state ) {
  75                         case READY:
  76                                 break;
  77
  78                         case WRITE:
  79                                 eecr->set( *eecr & CLEAR );
  80                                 writeToAddress( eear, *eedr );
  81
  82                                 if( (*eecr & EERIE) != 0 )
  83                                         bus.raiseInterrupt(rdyVec);
  84
  85                                 state = READY;
  86                                 break;
  87
  88                         case READ:
  89                                 eecr->set( *eecr & CLEAR );
  90                                 *eedr = readFromAddress( eear );
  91
  92                                 state = READY;
  93                                 break;
  94
  95                         case WRITE_ENABLED:
  96                                 eecr->set( *eecr & ~EEMWE );
  97                                 state = READY;
  98                                 break;
  99                 }
 100         }
 101
 102         void Eeprom::setEECR( unsigned char eecr ) {
 103             if( ((eecr & EEMWE) != 0) && (state == READY) ) {
 104                 state = WRITE_ENABLED;
 105                 bus.reassignBreakDelta(writeEnableCycles, this);
 106             } else if( ((eecr & EEWE) != 0) && (state == WRITE_ENABLED) ) {
 107                         state = WRITE;
 108                 setHoldCycles( writeCycles );
 109                         bus.reassignBreakDelta(writeCycles, this);
 110                 } else if( (eecr & EERE) != 0 ) {
 111                         //EERE EEprom read enable
 112                         if( state == WRITE ) {
 113                                 state = READ;
 114                                 bus.clearBreak(this);
 115                         } else {
 116                                 state = READ;
 117                                 setHoldCycles( readCycles );
 118                                 bus.reassignBreakDelta(readCycles, this);
 119                         }
 120
 121                         state = READ;
 122                 } else if( (eecr & 0x07) != 0x00 ) {
 123                 state = READY;
 124                 bus.clearBreak( this );
 125             }
 126
 127                 oldEecr = eecr;
 128         }
 129
 130 }