fdisk_memory.c

/*
  MEGA65 Memory Access routines that allow access to the full RAM of the MEGA65,
  even though the program is stuck living in the first 64KB of RAM, because CC65
  doesn't (yet) understand how to make multi-bank MEGA65 programs.

*/

#include "fdisk_memory.h"
#include "fdisk_screen.h"

struct dmagic_dmalist {
  // Enhanced DMA options
  unsigned char option_0b;
  unsigned char option_80;
  unsigned char source_mb;
  unsigned char option_81;
  unsigned char dest_mb;
  unsigned char end_of_options;

  // F018B format DMA request
  unsigned char command;
  unsigned int count;
  unsigned int source_addr;
  unsigned char source_bank;
  unsigned int dest_addr;
  unsigned char dest_bank;
  unsigned char sub_cmd; // F018B subcmd
  unsigned int modulo;
};

struct dmagic_dmalist dmalist;
unsigned char dma_byte;

#ifdef __CC65__
void do_dma(void)
{
  unsigned char i;
  m65_io_enable();

  //  for(i=0;i<24;i++)
  // screen_hex_byte(SCREEN_ADDRESS+i*3,PEEK(i+(unsigned int)&dmalist));

  // Now run DMA job (to and from anywhere, and list is in low 1MB)
  POKE(0xd702U, 0);
  POKE(0xd704U, 0x00); // List is in $00xxxxx
  POKE(0xd701U, ((unsigned int)&dmalist) >> 8);
  POKE(0xd705U, ((unsigned int)&dmalist) & 0xff); // triggers enhanced DMA
}

unsigned char lpeek(long address)
{
  // Read the byte at <address> in 28-bit address space
  // XXX - Optimise out repeated setup etc
  // (separate DMA lists for peek, poke and copy should
  // save space, since most fields can stay initialised).

  dmalist.option_0b = 0x0b;
  dmalist.option_80 = 0x80;
  dmalist.source_mb = (address >> 20);
  dmalist.option_81 = 0x81;
  dmalist.dest_mb = 0x00; // dma_byte lives in 1st MB
  dmalist.end_of_options = 0x00;

  dmalist.command = 0x00; // copy
  dmalist.count = 1;
  dmalist.source_addr = address & 0xffff;
  dmalist.source_bank = (address >> 16) & 0x7f;
  dmalist.dest_addr = (unsigned int)&dma_byte;
  dmalist.dest_bank = 0;

  do_dma();

  return dma_byte;
}

void lpoke(long address, unsigned char value)
{

  dmalist.option_0b = 0x0b;
  dmalist.option_80 = 0x80;
  dmalist.source_mb = 0x00; // dma_byte lives in 1st MB
  dmalist.option_81 = 0x81;
  dmalist.dest_mb = (address >> 20);
  dmalist.end_of_options = 0x00;

  dma_byte = value;
  dmalist.command = 0x00; // copy
  dmalist.count = 1;
  dmalist.source_addr = (unsigned int)&dma_byte;
  dmalist.source_bank = 0;
  dmalist.dest_addr = address & 0xffff;
  dmalist.dest_bank = (address >> 16) & 0x7f;

  do_dma();
  return;
}

void lcopy(long source_address, long destination_address, unsigned int count)
{
  dmalist.option_0b = 0x0b;
  dmalist.option_80 = 0x80;
  dmalist.source_mb = source_address >> 20;
  dmalist.option_81 = 0x81;
  dmalist.dest_mb = (destination_address >> 20);
  dmalist.end_of_options = 0x00;

  dmalist.command = 0x00; // copy
  dmalist.count = count;
  dmalist.sub_cmd = 0;
  dmalist.source_addr = source_address & 0xffff;
  dmalist.source_bank = (source_address >> 16) & 0x0f;
  if (source_address >= 0xd000 && source_address < 0xe000)
    dmalist.source_bank |= 0x80;
  dmalist.dest_addr = destination_address & 0xffff;
  dmalist.dest_bank = (destination_address >> 16) & 0x0f;
  if (destination_address >= 0xd000 && destination_address < 0xe000)
    dmalist.dest_bank |= 0x80;

  do_dma();
  return;
}

void lfill(long destination_address, unsigned char value, unsigned int count)
{
  dmalist.option_0b = 0x0b;
  dmalist.option_80 = 0x80;
  dmalist.source_mb = 0x00;
  dmalist.option_81 = 0x81;
  dmalist.dest_mb = destination_address >> 20;
  dmalist.end_of_options = 0x00;

  dmalist.command = 0x03; // fill
  dmalist.sub_cmd = 0;
  dmalist.count = count;
  dmalist.source_addr = value;
  dmalist.dest_addr = destination_address & 0xffff;
  dmalist.dest_bank = (destination_address >> 16) & 0x7f;
  if (destination_address >= 0xd000 && destination_address < 0xe000)
    dmalist.dest_bank |= 0x80;

  do_dma();
  return;
}

void m65_io_enable(void)
{
  // Gate C65 IO enable
  POKE(0xd02fU, 0x47);
  POKE(0xd02fU, 0x53);
  // Force to full speed
  POKE(0, 65);
}
#else
#include <string.h>

void m65_io_enable(void)
{
}

void lfill(long destination_address, unsigned char value, unsigned int count)
{
  memset((void*)destination_address, value, count);
}

void lcopy(long source_address, long destination_address, unsigned int count)
{
  memcpy((void*)destination_address, (void*)source_address, count);
}
#endif