55 lines
1.0 KiB
C
55 lines
1.0 KiB
C
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#include <string.h>
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#include "tms9918.h"
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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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}
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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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}
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}
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uint8_t tms_data_rd(TMS9918 *tms)
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{
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if (tms->curaddr < TMS_VRAM_SIZE) {
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return tms->vram[tms->curaddr++];
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} else {
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return 0;
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}
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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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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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return 0; // no TMS9918 mode implemented yet
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}
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