8bitworkshop/presets/coleco/mode2bitmap.c

/*
Displays a bitmap using the TMS9928A's Mode 2.

In Mode 2, the screen is horizontally divided into three
256×64 pixel areas, each of which gets its own character
set. By sequentially printing the characters 0 through 255
in all three areas, the program can simulate a graphics mode
where each pixel can be set individually.

The limitation is that every horizontal run of 8 pixels
can only have two colors (a foreground and background color.)

The included Mode 2 bitmap was converted with a web utility:
http://msx.jannone.org/conv/
*/

#include <stdlib.h>

#include <cv.h>
#include <cvu.h>

#include "common.h"

/* link in MODE 2 bitmap data */

//#link "sailboat.s"

extern const unsigned char msx_bitmap[0x3807];

void setup_mode2() {
  cvu_vmemset(0, 0, 0x4000);
  cv_set_screen_mode(CV_SCREENMODE_BITMAP); // mode 2
  cv_set_image_table(IMAGE);
  cv_set_character_pattern_t(PATTERN|0x1fff); // AND mask
  cv_set_color_table(COLOR|0x1fff); // AND mask
  cv_set_sprite_attribute_table(SPRITES);
}

void main() {
  // turn off screen
  cv_set_screen_active(false);
  // setup mode 2 grpahics
  setup_mode2();
  // copy pattern and color tables
  cvu_memtovmemcpy(PATTERN, msx_bitmap+7, 0x1800);
  cvu_memtovmemcpy(COLOR, msx_bitmap+7+COLOR, 0x1800);
  // set IMAGE table to incrementing values
  for (int i=0; i<0x300; i++) {
    	cvu_voutb(i, IMAGE+i);
  }
  // clear sprite table
  cvu_vmemset(SPRITES, 0, 0x100);
  // turn off screen
  cv_set_screen_active(true);
  while (1) {
    //cv_set_character_pattern_t(PATTERN|rand()); // AND mask
    //cv_set_color_table(COLOR|rand()); // AND mask
  }
}