mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-24 07:28:06 +11:00
83 lines
2.1 KiB
C
83 lines
2.1 KiB
C
#include <string.h>
|
|
#include "vdp.h"
|
|
|
|
void vdp_init(VDP *vdp)
|
|
{
|
|
memset(vdp->vram, 0, VDP_VRAM_SIZE);
|
|
memset(vdp->regs, 0, 0x10);
|
|
vdp->has_cmdlsb = false;
|
|
vdp->curaddr = 0;
|
|
}
|
|
|
|
uint8_t vdp_cmd_rd(VDP *vdp)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
void vdp_cmd_wr(VDP *vdp, uint8_t val)
|
|
{
|
|
if (!vdp->has_cmdlsb) {
|
|
vdp->cmdlsb = val;
|
|
vdp->has_cmdlsb = true;
|
|
return;
|
|
}
|
|
vdp->has_cmdlsb = false;
|
|
if ((val & 0xc0) == 0x80) {
|
|
// set register
|
|
vdp->regs[val&0xf] = vdp->cmdlsb;
|
|
} else if ((val & 0xc0) == 0xc0) {
|
|
// palette RAM
|
|
vdp->curaddr = 0x4000 + (vdp->cmdlsb&0x1f);
|
|
} else {
|
|
// VRAM
|
|
vdp->curaddr = ((val&0x3f) << 8) + vdp->cmdlsb;
|
|
}
|
|
}
|
|
|
|
uint8_t vdp_data_rd(VDP *vdp)
|
|
{
|
|
uint8_t res = vdp->vram[vdp->curaddr];
|
|
if (vdp->curaddr < VDP_VRAM_SIZE) {
|
|
vdp->curaddr++;
|
|
}
|
|
return res;
|
|
}
|
|
|
|
void vdp_data_wr(VDP *vdp, uint8_t val)
|
|
{
|
|
vdp->vram[vdp->curaddr] = val;
|
|
if (vdp->curaddr < VDP_VRAM_SIZE) {
|
|
vdp->curaddr++;
|
|
}
|
|
}
|
|
|
|
// Returns a 8-bit RGB value (0b00bbggrr)
|
|
uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
|
|
{
|
|
if (x >= VDP_SCREENW) {
|
|
return 0;
|
|
}
|
|
if (y >= VDP_SCREENH) {
|
|
return 0;
|
|
}
|
|
// name table offset
|
|
uint16_t offset = 0x3800 + ((y/8) << 6) + ((x/8) << 1);
|
|
uint16_t tableval = vdp->vram[offset] + (vdp->vram[offset+1] << 8);
|
|
uint16_t tilenum = tableval & 0x1ff;
|
|
// is palette select bit on? if yes, use sprite palette instead
|
|
uint8_t palettemod = tableval & 0x800 ? 0x10 : 0;
|
|
// tile offset this time. Each tile is 0x20 bytes long.
|
|
offset = tilenum * 0x20;
|
|
// Each 4 byte is a row. Find row first.
|
|
offset += ((y%8) * 4);
|
|
uint8_t bitnum = 7 - (x%8);
|
|
// Now, let's compose the result by pushing the right bit of our 4 bytes
|
|
// into our result.
|
|
uint8_t palette_id = ((vdp->vram[offset] >> bitnum) & 1) + \
|
|
(((vdp->vram[offset+1] >> bitnum) & 1) << 1) + \
|
|
(((vdp->vram[offset+2] >> bitnum) & 1) << 2) + \
|
|
(((vdp->vram[offset+3] >> bitnum) & 1) << 3);
|
|
uint8_t rgb = vdp->vram[0x4000+palettemod+palette_id];
|
|
return rgb;
|
|
}
|