host_mega.cpp

// -----------------------------------------------------------------------------
// Altair 8800 Simulator
// Copyright (C) 2017 David Hansel
//
// This program 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.
//
// This program 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 this program; if not, write to the Free Software Foundation,
// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
// -----------------------------------------------------------------------------

#ifdef __AVR_ATmega2560__

#include <Arduino.h>
#include "Altair8800.h"
#include "config.h"
#include "mem.h"
#include "host_mega.h"


#if NUM_DRIVES>0 || NUM_TDRIVES>0 || NUM_CDRIVES>0
#error Arduino MEGA port does not support disk drives. Set NUM_DRIVES, NUM_TDRIVES and NUM_CDRIVES to 0 in config.h
#endif

#if NUM_HDSK_UNITS>0
#error Arduino MEGA port does not support hard disks. Set NUM_HDSK_UNITS to 0 in config.h
#endif

#if USE_THROTTLE>0
#error Throttling neither supported nor necessary for Arduino MEGA. Set USE_THROTTLE to 0 in config.h
#endif

#if USE_HOST_FILESYS>0
#error Arduino MEGA does not supply a filesystem. Set USE_HOST_FILESYS to 0 in config.h
#endif

#if USE_PRINTER>0 && MEMSIZE>(4096+1024)
#error Either set USE_PRINTER to 0 in config.h or reduce MEMSIZE in host_mega.h to 4096+1024, otherwise stability problems may occur
#endif

#if USE_DAZZLER>0
#error Arduino MEGA does not support DAZZLER emulation
#endif

#if USE_VDM1>0
#error Arduino MEGA does not support VDM-1 emulation
#endif

#if MAX_NUM_ROMS>1
#error MAX_NUM_ROMS>1 is NOT recommended due to memory constraints. See comment in host_mega.h
#endif

#if USE_Z80==2
#error Arduino MEGA does not support dynamic processor switching
#endif

/*
  Runs emulation at about 0.5 Mhz clock speed (about 1/4 speed of original Altair8800)

  Function switch pin mapping (digital input):
     RUN          => 20
     STOP         => 21 (Port D, bit 0)
     STEP         =>  4
     SLOW         =>  5
     EXAMINE      =>  6
     EXAMINE NEXT =>  7
     DEPOSIT      =>  8
     DEPOSIT NEXT =>  9
     RESET        => 18 (Port D, bit 3)
     CLR          => 19 (Port D, bit 2)
     PROTECT      => 16
     UNPROTECT    => 17
     AUX1 UP      => 14
     AUX1 DOWN    => 15
     AUX2 UP      =>  3 (PORT E, bit 5)
     AUX2 DOWN    =>  2 (PORT E, bit 4)

   Address/Data switch pin mapping (analog input):
     A0...15      => A0...15

   Status LED mapping (digital output):
    +A0..7        => 22, 23, ..., 29  (PORTA)
    +A8..15       => 37, 36, ..., 30  (PORTC)
    +D0..8        => 49, 48, ..., 42  (PORTL)
    *INT          => 53 \
     WO           => 52 |
     STACK        => 51 |
     HLTA         => 50 | STATUS      (PORTB)
     OUT          => 10 |
     M1           => 11 |
     INP          => 12 |
     MEMR         => 13 /
     INTE         => 38
     PROT         => 39
     WAIT         => 40
    *HLDA         => 41

*/


uint16_t host_read_status_leds()
{
  uint16_t res = PORTB;
  res |= PORTD & 0x80 ? ST_INTE : 0;
  res |= PORTG & 0x04 ? ST_PROT : 0;
  res |= PORTG & 0x02 ? ST_WAIT : 0;
  res |= PORTG & 0x01 ? ST_HLDA : 0;
  return res;
}


//------------------------------------------------------------------------------------------------------


bool host_storage_init(bool write)
{
  return true;
}


void host_storage_close()
{}


void host_storage_invalidate()
{}


void host_storage_write(const void *data, uint32_t addr, uint32_t len)
{
  byte *b = (byte *) data;
  for(uint32_t i=0; i<len; i++) EEPROM.write(addr+i, b[i]);
}


void host_storage_read(void *data, uint32_t addr, uint32_t len)
{
  byte *b = (byte *) data;
  for(uint32_t i=0; i<len; i++) b[i] = EEPROM.read(addr+i);
}


void host_storage_move(uint32_t to, uint32_t from, uint32_t len)
{
  uint32_t i;
  if( from<to )
    {
      for(i=0; i<len; i++) EEPROM.write(to+len-i-1, EEPROM.read(from+len-i-1));
    }
  else
    {
      for(i=0; i<len; i++) EEPROM.write(to+i, EEPROM.read(from+i));
    }
}


// --------------------------------------------------------------------------------------------------


uint32_t host_get_random()
{
  return (((uint32_t) random(0,65535)) * 65536l | random(0,65535));
}


void host_copy_flash_to_ram(void *dst, const void *src, uint32_t len)
{
  for(uint32_t i=0; i<len; i++) 
    ((byte *) dst)[i] = pgm_read_byte(((byte *) src)+i);
}


// --------------------------------------------------------------------------------------------------


volatile static uint16_t switches_pulse = 0;
volatile static uint16_t switches_debounced = 0;
static uint32_t debounceTime[8];
const PROGMEM uint8_t function_switch_pins[16] = {20, 21, 4, 5, 6, 7, 8, 9, 18, 19, 16, 17, 14, 15, 3, 2};
const PROGMEM uint8_t function_switch_irqs[16] = {0, INT_SW_STOP>>24, 0, 0, 0, 0, 0, 0, 
                                                  INT_SW_RESET>>24, INT_SW_CLR>>24, 0, 0, 0, 0, 
                                                  INT_SW_AUX2UP>>24, INT_SW_AUX2DOWN>>24};

byte function_switch_pin(byte i)
{
  return pgm_read_byte_near(function_switch_pins + i);
}


byte function_switch_irq(byte i)
{
  return pgm_read_byte_near(function_switch_irqs + i);
}


static void switch_check(byte i)
{
  if( millis()>debounceTime[i/2] )
    {
      uint16_t bitval = 1<<i;
      bool d1 = !digitalRead(function_switch_pin(i));
      bool d2 = (switches_debounced & bitval) ? true : false;

      if( d1 && !d2 ) 
        {
          switches_debounced |= bitval;
          switches_pulse     |= bitval;
          if( function_switch_irq(i) ) altair_interrupt(((uint32_t) function_switch_irq(i))<<24);
          debounceTime[i/2] = millis() + 100;
        }
      else if( !d1 && d2 ) 
        {
          switches_debounced &= ~bitval;
          switches_pulse     &= ~bitval;
          debounceTime[i/2] = millis() + 100;
        }
    }
}


bool host_read_function_switch(byte i)
{
  return !digitalRead(function_switch_pin(i));
}


bool host_read_function_switch_debounced(byte i)
{
  if( function_switch_irq(i)==0 ) switch_check(i);
  return (switches_debounced & (1<<i)) ? true : false;
}


bool host_read_function_switch_edge(byte i)
{
  if( function_switch_irq(i)==0 ) switch_check(i);
  uint16_t bitval = 1<<i;
  bool b = switches_pulse & bitval ? true : false;
  if( b ) switches_pulse &= ~bitval;
  return b;
}


uint16_t host_read_function_switches_edge()
{
  for(byte i=0; i<16; i++) 
    if( function_switch_irq(i)==0 ) 
      switch_check(i);

  uint16_t res = switches_pulse;
  switches_pulse &= ~res;
  return res;
}


void host_reset_function_switch_state()
{
  for(byte i=0; i<8; i++) debounceTime[i]=0;
  switches_debounced = 0;
  switches_pulse     = 0;
}


static void switch_interrupt(int i)
{
  switch_check(i);
}  


static void switch_interrupt1() { switch_interrupt(SW_STOP);     }
static void switch_interrupt2() { switch_interrupt(SW_RESET);    }
static void switch_interrupt3() { switch_interrupt(SW_CLR);      }
static void switch_interrupt4() { switch_interrupt(SW_AUX2UP);   }
static void switch_interrupt5() { switch_interrupt(SW_AUX2DOWN); }


static void switches_setup()
{
  attachInterrupt(digitalPinToInterrupt(function_switch_pin(SW_STOP)),     switch_interrupt1, CHANGE);
  attachInterrupt(digitalPinToInterrupt(function_switch_pin(SW_RESET)),    switch_interrupt2, CHANGE);
  attachInterrupt(digitalPinToInterrupt(function_switch_pin(SW_CLR)),      switch_interrupt3, CHANGE);
  attachInterrupt(digitalPinToInterrupt(function_switch_pin(SW_AUX2UP)),   switch_interrupt4, CHANGE);
  attachInterrupt(digitalPinToInterrupt(function_switch_pin(SW_AUX2DOWN)), switch_interrupt5, CHANGE);

  delay(1);
  host_reset_function_switch_state();
}


// --------------------------------------------------------------------------------------------------


void host_serial_setup(byte iface, uint32_t baud, uint32_t config, bool set_primary_interface)
{
  if( iface==0 )
    {
      Serial.end();
      Serial.begin(baud, config);
      Serial.setTimeout(10000);
    }
}


int host_serial_available_for_write(byte i)
{
  return Serial.availableForWrite();
}


size_t host_serial_write(byte i, uint8_t b)
{
  Serial.write(b);
}


const char *host_serial_port_name(byte i)
{
  return "Serial";
}


bool host_serial_port_baud_limits(byte i, uint32_t *min, uint32_t *max)
{
  if( i==0 )
    {
      *min = 600; 
      *max = 115200;
      return true;
    }
  else
    return false;
}


bool host_serial_port_has_configs(byte i)
{
#if USE_SERIAL_CONFIGS>0
  return i==0;
#else
  return false;
#endif
}

bool host_serial_port_support_xonxoff(byte i)
{
  return false;
}


static void printHex(int i) { if( i<0x1000 ) Serial.print('0'); Serial.println(i, HEX); }
void host_system_info()
{
  extern int __bss_end, __heap_start, *__brkval; 
  int ramstart = 0x0200;
  int bssend   = (int) &__bss_end;
  int heapend  = __brkval == 0 ? (int) &__heap_start : (int) __brkval;
  int ramend   = 0x2200;

  Serial.println(F("Host is Arduino Mega 2560\n"));
  Serial.print(F("RAM Start        : 0x")); printHex(ramstart);
  Serial.print(F("Data/Bss end     : 0x")); printHex(bssend);
  Serial.print(F("Heap End         : 0x")); printHex(heapend);
  Serial.print(F("Stack Pointer    : 0x")); printHex(SP);
  Serial.print(F("RAM End          : 0x")); printHex(ramend);
  Serial.print(F("Program RAM Used : ")); Serial.println(bssend - ramstart);
  Serial.print(F("Heap RAM Used    : ")); Serial.println(heapend - bssend);
  Serial.print(F("Stack RAM Used   : ")); Serial.println(ramend - SP);
  Serial.print(F("Free RAM         : ")); Serial.println(SP - heapend);
}


void host_setup()
{
  int i;
  for(i=0; i<8; i++)
    {
      pinMode(2+i,  INPUT_PULLUP);  
      pinMode(14+i, INPUT_PULLUP);
    }
  for(i=10; i<14; i++) pinMode(i, OUTPUT);
  for(i=22; i<54; i++) pinMode(i, OUTPUT);

  switches_setup();

  // TODO: Find a way to initialize random number generator. Unfortunately 
  //       this is hard since all analog pins are connected and therefore the 
  //       usual analogRead(0) method always returns either 0 or 1023, depending
  //       on the setting of SW0
  randomSeed(analogRead(0));
}

#endif