72 lines
1.7 KiB
C
72 lines
1.7 KiB
C
#include <cpu.h>
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#include <bus.h>
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cpu_context ctx = {0};
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void cpu_init() {
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ctx.regs.pc = 0x100;
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}
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static void fetch_instruction() {
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ctx.cur_opcode = bus_read(ctx.regs.pc++);
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ctx.cur_inst = instruction_by_opcode(ctx.cur_opcode);
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}
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static void fetch_data() {
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ctx.mem_dest = 0;
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ctx.dest_is_mem = false;
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if(ctx.cur_inst == NULL) return;
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switch(ctx.cur_inst->mode) {
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case AM_IMP: return;
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case AM_R:
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ctx.fetched_data = cpu_read_reg(ctx.cur_inst->reg_1);
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return;
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case AM_R_D8:
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ctx.fetched_data = bus_read(ctx.regs.pc);
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emu_cycles(1);
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ctx.regs.pc++;
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return;
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case AM_D16: {
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u16 lo = bus_read(ctx.regs.pc);
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emu_cycles(1);
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u16 hi = bus_read(ctx.regs.pc+1);
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emu_cycles(1);
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ctx.fetched_data = lo | (hi << 8);
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ctx.regs.pc += 2;
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return;
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}
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default:
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printf("Unknown Addressing Mode! %d\n", ctx.cur_inst->mode);
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exit(-7);
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return;
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}
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}
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static void execute() {
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IN_PROC proc = inst_get_processor(ctx.cur_inst->type);
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if (!proc) {
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NO_IMPL
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}
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proc(&ctx);
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}
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bool cpu_step() {
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if(!ctx.halted) {
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u16 pc = ctx.regs.pc;
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fetch_instruction();
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fetch_data();
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printf("%04X: %7s (%02X %02X %02X) A: %02X B: %02X C: %02X\n", pc, ctx.cur_inst != NULL ? inst_name(ctx.cur_inst->type) : "UNK", ctx.cur_opcode, bus_read(pc+1), bus_read(pc+2), ctx.regs.a, ctx.regs.b, ctx.regs.c);
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if(ctx.cur_inst == NULL){
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printf("Unknown Instruction! %02X\n", ctx.cur_opcode);
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exit(-7);
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}
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execute();
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}
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return true;
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} |