81 lines
1.6 KiB
C
81 lines
1.6 KiB
C
#include <stdint.h>
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#include "config.h"
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extern void scanKeyboard();
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extern void writeVideo();
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extern uint8_t readVideo();
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extern uint8_t videoX;
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extern uint8_t videoY;
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extern uint8_t videoMode;
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extern uint8_t videoA;
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static int8_t ram[RAMSIZE + 1];
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static int8_t rom[ROMSIZE + 1];
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static uint8_t systemRegister;
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static uint8_t keyboardResult;
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uint8_t read6502(uint16_t address);
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void write6502(uint16_t address, uint8_t value);
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uint8_t read6502(uint16_t address){
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switch (address){
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case RAMLOC ... RAMLOC + RAMSIZE:
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return ram[address - RAMLOC];
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break;
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case ROMLOC ... ROMLOC + ROMSIZE:
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return rom[address - ROMLOC];
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break;
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case VIDADDRS ... VIDADDRS + PAGESIZE:
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if ((address - VIDADDRS) % 4 == 3) return readVideo();
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else return 0;
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break;
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case 0xBD00:
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scanKeyboard();
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return keyboardResult;
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break;
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default: return NOP;
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}
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}
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void write6502(uint16_t address, uint8_t value){
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switch (address){
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case RAMLOC ... RAMLOC + RAMSIZE:
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ram[address - RAMLOC] = value;
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break;
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case ROMLOC ... ROMLOC + ROMSIZE:
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rom[address - ROMLOC] = value;
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break;
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case VIDADDRS ... VIDADDRS + PAGESIZE:
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switch ((address - VIDADDRS) % 4){
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case 0: /* Video X Register */
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videoX = value & 0b01111111;
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break;
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case 1: /* Video Y Register */
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videoY = value;
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break;
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case 2: /* Video M Register */
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videoMode = value;
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break;
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case 3: /* Video A Register */
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videoA = value;
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writeVideo();
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break;
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}
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break;
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case 0xBC00:
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systemRegister = value;
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break;
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default: break;
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}
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}
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