mirror of https://github.com/hsoft/collapseos.git
92 lines
2.0 KiB
C
92 lines
2.0 KiB
C
#include <stdio.h>
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#include <string.h>
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#include "tms9918.h"
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static uint8_t COLORS[0x10] = { // TODO: put actual color codes
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0, // transparent
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0, // black
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1, // medium green
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1, // light green
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1, // dark blue
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1, // light blue
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1, // dark red
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1, // cyan
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1, // medium red
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1, // light red
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1, // dark yellow
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1, // light yellow
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1, // dark green
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1, // magenta
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1, // gray
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1, // white
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};
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void tms_init(TMS9918 *tms)
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{
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memset(tms->vram, 0, TMS_VRAM_SIZE);
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memset(tms->regs, 0, 0x10);
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tms->has_cmdlsb = false;
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tms->curaddr = 0;
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tms->databuf = 0;
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tms->width = 40*6;
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tms->height = 24*8;
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}
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uint8_t tms_cmd_rd(TMS9918 *tms)
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{
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return 0;
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}
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void tms_cmd_wr(TMS9918 *tms, uint8_t val)
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{
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if (!tms->has_cmdlsb) {
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tms->cmdlsb = val;
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tms->has_cmdlsb = true;
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return;
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}
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tms->has_cmdlsb = false;
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if ((val & 0xc0) == 0x80) {
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// set register
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tms->regs[val&0xf] = tms->cmdlsb;
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} else {
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// VRAM
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tms->curaddr = ((val&0x3f) << 8) + tms->cmdlsb;
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if ((val & 0x40) == 0) { // reading VRAM
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tms->databuf = tms->vram[tms->curaddr];
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}
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}
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}
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uint8_t tms_data_rd(TMS9918 *tms)
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{
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return tms->databuf;
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}
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void tms_data_wr(TMS9918 *tms, uint8_t val)
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{
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tms->databuf = val;
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if (tms->curaddr < TMS_VRAM_SIZE) {
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tms->vram[tms->curaddr++] = val;
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}
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}
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// Returns a 8-bit RGB value (0b00bbggrr)
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uint8_t tms_pixel(TMS9918 *tms, uint16_t x, uint16_t y)
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{
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if ((tms->regs[1]&0x18) == 0x10 && (tms->regs[0]&0x40) == 0) {
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// Text mode
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uint16_t nameoff = (tms->regs[2] & 0xf) << 10;
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uint16_t patternoff = (tms->regs[4] & 0x7) << 11;
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uint8_t nameid = tms->vram[nameoff+(((y/8) * 40) + (x/6))];
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uint8_t patternline = tms->vram[patternoff+(nameid*8)+(y%8)];
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uint8_t color = tms->regs[7];
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if ((patternline>>(8-(x%6)))&1) {
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color >>= 4;
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}
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color &= 0xf;
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return color;
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} else { // unsupported mode
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return 0;
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}
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}
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