mirror of https://github.com/hsoft/collapseos.git
86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
#include <string.h>
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#include "sms_vdp.h"
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static bool _is_mode4(VDP *vdp)
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{
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return (vdp->tms.regs[0]&0x4);
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}
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void vdp_init(VDP *vdp)
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{
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tms_init(&vdp->tms);
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memset(vdp->cram, 0, VDP_CRAM_SIZE);
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}
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void vdp_cmd_wr(VDP *vdp, uint8_t val)
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{
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if (!vdp->tms.has_cmdlsb) {
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tms_cmd_wr(&vdp->tms, val);
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} else {
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if ((val & 0xc0) == 0xc0) {
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// palette RAM
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// curaddr > VRAM == addr in CRAM
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vdp->tms.curaddr = TMS_VRAM_SIZE + (vdp->tms.cmdlsb&0x1f);
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} else {
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tms_cmd_wr(&vdp->tms, val);
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vdp->tms.width = _is_mode4(vdp) ? 32*8 : 40*6;
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}
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}
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}
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uint8_t vdp_data_rd(VDP *vdp)
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{
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TMS9918 *tms = &vdp->tms;
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if (tms->curaddr < TMS_VRAM_SIZE) {
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return tms_data_rd(&vdp->tms);
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} else if (tms->curaddr - TMS_VRAM_SIZE < VDP_CRAM_SIZE) {
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return vdp->cram[tms->curaddr++-TMS_VRAM_SIZE];
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} else {
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return 0;
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}
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}
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void vdp_data_wr(VDP *vdp, uint8_t val)
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{
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TMS9918 *tms = &vdp->tms;
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if (tms->curaddr < TMS_VRAM_SIZE) {
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tms_data_wr(&vdp->tms, val);
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} else if (tms->curaddr - TMS_VRAM_SIZE < VDP_CRAM_SIZE) {
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vdp->cram[tms->curaddr++-TMS_VRAM_SIZE] = val;
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}
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}
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uint8_t vdp_pixel(VDP *vdp, uint16_t x, uint16_t y)
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{
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TMS9918 *tms = &vdp->tms;
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if (!_is_mode4(vdp)) {
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return tms_pixel(tms, x, y);
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}
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if (x >= tms->width) {
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return 0;
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}
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if (y >= tms->height) {
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return 0;
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}
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// name table offset
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uint16_t offset = (tms->regs[2] & 0xe) << 10;
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offset += ((y/8) << 6) + ((x/8) << 1);
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uint16_t tableval = tms->vram[offset] + (tms->vram[offset+1] << 8);
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uint16_t tilenum = tableval & 0x1ff;
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// is palette select bit on? if yes, use sprite palette instead
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uint8_t palettemod = tableval & 0x800 ? 0x10 : 0;
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// tile offset this time. Each tile is 0x20 bytes long.
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offset = tilenum * 0x20;
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// Each 4 byte is a row. Find row first.
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offset += ((y%8) * 4);
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uint8_t bitnum = 7 - (x%8);
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// Now, let's compose the result by pushing the right bit of our 4 bytes
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// into our result.
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uint8_t palette_id = ((tms->vram[offset] >> bitnum) & 1) + \
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(((tms->vram[offset+1] >> bitnum) & 1) << 1) + \
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(((tms->vram[offset+2] >> bitnum) & 1) << 2) + \
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(((tms->vram[offset+3] >> bitnum) & 1) << 3);
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uint8_t rgb = vdp->cram[palettemod+palette_id];
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return rgb;
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}
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