241 lines
6.9 KiB
C
241 lines
6.9 KiB
C
#include <stdio.h>
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/*
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Copyright (c) 2021 Devine Lu Linvega
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE.
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*/
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#include "cpu.h"
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#define FLAG_HALT 0x01
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#define FLAG_SHORT 0x02
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#define FLAG_SIGN 0x04
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#define FLAG_COND 0x08
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Computer cpu;
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#pragma mark - Helpers
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void
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setflag(char flag, int b)
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{
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if(b)
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cpu.status |= flag;
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else
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cpu.status &= (~flag);
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}
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int
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getflag(char flag)
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{
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return cpu.status & flag;
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}
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void
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echos(Stack8 *s, Uint8 len, char *name)
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{
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int i;
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printf("\n%s\n", name);
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for(i = 0; i < len; ++i) {
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if(i % 16 == 0)
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printf("\n");
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printf("%02x%c", s->dat[i], s->ptr == i ? '<' : ' ');
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}
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printf("\n\n");
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}
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void
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echom(Memory *m, Uint8 len, char *name)
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{
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int i;
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printf("\n%s\n", name);
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for(i = 0; i < len; ++i) {
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if(i % 16 == 0)
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printf("\n");
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printf("%02x ", m->dat[i]);
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}
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printf("\n\n");
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}
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#pragma mark - Operations
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/* clang-format off */
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Uint16 bytes2short(Uint8 a, Uint8 b) { return (a << 8) + b; }
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Uint16 mempeek16(Uint16 s) { return (cpu.ram.dat[s] << 8) + (cpu.ram.dat[s+1] & 0xff); }
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void wspush8(Uint8 b) { cpu.wst.dat[cpu.wst.ptr++] = b; }
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void wspush16(Uint16 s) { wspush8(s >> 8); wspush8(s & 0xff); }
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Uint8 wspop8(void) { return cpu.wst.dat[--cpu.wst.ptr]; }
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Uint16 wspop16(void) { return wspop8() + (wspop8() << 8); }
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Uint8 wspeek8(Uint8 o) { return cpu.wst.dat[cpu.wst.ptr - o]; }
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Uint16 wspeek16(Uint8 o) { return bytes2short(cpu.wst.dat[cpu.wst.ptr - o], cpu.wst.dat[cpu.wst.ptr - o + 1]); }
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Uint16 rspop16(void) { return cpu.rst.dat[--cpu.rst.ptr]; }
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void rspush16(Uint16 a) { cpu.rst.dat[cpu.rst.ptr++] = a; }
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/* I/O */
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void op_brk() { setflag(FLAG_HALT, 1); }
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void op_lit() { cpu.literal += cpu.ram.dat[cpu.ram.ptr++]; }
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void op_nop() { printf("NOP");}
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void op_ldr() { wspush8(cpu.ram.dat[wspop16()]); }
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void op_str() { cpu.ram.dat[wspop16()] = wspop8(); }
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/* Logic */
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void op_jmp() { cpu.ram.ptr = wspop16(); }
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void op_jsr() { rspush16(cpu.ram.ptr); cpu.ram.ptr = wspop16(); }
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void op_rts() { cpu.ram.ptr = rspop16(); }
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/* Stack */
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void op_pop() { wspop8(); }
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void op_dup() { wspush8(wspeek8(1)); }
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void op_swp() { Uint8 b = wspop8(), a = wspop8(); wspush8(b); wspush8(a); }
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void op_ovr() { Uint8 a = wspeek8(2); wspush8(a); }
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void op_rot() { Uint8 c = wspop8(),b = wspop8(),a = wspop8(); wspush8(b); wspush8(c); wspush8(a); }
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void op_and() { Uint8 a = wspop8(), b = wspop8(); wspush8(a & b); }
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void op_ora() { Uint8 a = wspop8(), b = wspop8(); wspush8(a | b); }
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void op_rol() { Uint8 a = wspop8(), b = wspop8(); wspush8(a << b); }
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/* Arithmetic */
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void op_add() { Uint8 a = wspop8(), b = wspop8(); wspush8(b + a); }
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void op_sub() { Uint8 a = wspop8(), b = wspop8(); wspush8(b - a); }
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void op_mul() { Uint8 a = wspop8(), b = wspop8(); wspush8(b * a); }
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void op_div() { Uint8 a = wspop8(), b = wspop8(); wspush8(b / a); }
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void op_equ() { Uint8 a = wspop8(), b = wspop8(); wspush8(b == a); }
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void op_neq() { Uint8 a = wspop8(), b = wspop8(); wspush8(b != a); }
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void op_gth() { Uint8 a = wspop8(), b = wspop8(); wspush8(b > a); }
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void op_lth() { Uint8 a = wspop8(), b = wspop8(); wspush8(b < a); }
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/* Stack(16-bits) */
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void op_pop16() { wspop16(); }
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void op_dup16() { wspush16(wspeek16(2)); }
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void op_swp16() { Uint16 b = wspop16(), a = wspop16(); wspush16(b); wspush16(a); }
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void op_ovr16() { Uint16 a = wspeek16(4); wspush16(a); }
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void op_rot16() { Uint16 c = wspop16(), b = wspop16(), a = wspop16(); wspush16(b); wspush16(c); wspush16(a); }
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void op_and16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a & b); }
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void op_ora16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a | b); }
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void op_rol16() { Uint16 a = wspop16(), b = wspop16(); wspush16(a << b); }
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/* Arithmetic(16-bits) */
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void op_add16() { Uint16 a = wspop16(), b = wspop16(); wspush16(b + a); }
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void op_sub16() { Uint16 a = wspop16(), b = wspop16(); wspush16(b - a); }
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void op_mul16() { Uint16 a = wspop16(), b = wspop16(); wspush16(b * a); }
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void op_div16() { Uint16 a = wspop16(), b = wspop16(); wspush16(b / a); }
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void op_equ16() { Uint16 a = wspop16(), b = wspop16(); wspush8(b == a); }
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void op_neq16() { Uint16 a = wspop16(), b = wspop16(); wspush8(b != a); }
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void op_gth16() { Uint16 a = wspop16(), b = wspop16(); wspush8(b > a); }
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void op_lth16() { Uint16 a = wspop16(), b = wspop16(); wspush8(b < a); }
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void (*ops[])() = {
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op_brk, op_lit, op_nop, op_nop, op_nop, op_nop, op_ldr, op_str,
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op_jmp, op_jsr, op_nop, op_rts, op_nop, op_nop, op_nop, op_nop,
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op_pop, op_dup, op_swp, op_ovr, op_rot, op_and, op_ora, op_rol,
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op_add, op_sub, op_mul, op_div, op_equ, op_neq, op_gth, op_lth,
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op_pop16, op_dup16, op_swp16, op_ovr16, op_rot16, op_and16, op_ora16, op_rol16,
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op_add16, op_sub16, op_mul16, op_div16, op_equ16, op_neq16, op_gth16, op_lth16
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};
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Uint8 opr[][2] = {
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{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {2,1}, {3,0},
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{2,0}, {2,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0},
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{1,0}, {1,2}, {2,2}, {3,3}, {3,3}, {2,1}, {2,1}, {2,1},
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{2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1}, {2,1},
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{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, /* TODO */
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{0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0}, {0,0} /* TODO */
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};
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/* clang-format on */
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int
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error(char *name, int id)
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{
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printf("Error: %s[%04x], at 0x%04x\n", name, id, cpu.counter);
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return 0;
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}
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int
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doliteral(Uint8 instr)
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{
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if(cpu.wst.ptr >= 255)
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return error("Stack overflow", instr);
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wspush8(instr);
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cpu.literal--;
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return 1;
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}
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int
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dodevices(void) /* experimental */
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{
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if(cpu.ram.dat[0xfff1]) {
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printf("%c", cpu.ram.dat[0xfff1]);
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cpu.ram.dat[0xfff1] = 0x00;
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}
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return 1;
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}
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int
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doopcode(Uint8 instr)
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{
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Uint8 op = instr & 0x1f;
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setflag(FLAG_SHORT, (instr >> 5) & 1);
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setflag(FLAG_SIGN, (instr >> 6) & 1); /* usused */
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setflag(FLAG_COND, (instr >> 7) & 1);
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if(getflag(FLAG_SHORT))
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op += 16;
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if(cpu.wst.ptr < opr[op][0])
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return error("Stack underflow", op);
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if(cpu.wst.ptr + opr[op][1] - opr[op][0] >= 255)
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return error("Stack overflow", instr);
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if(!getflag(FLAG_COND) || (getflag(FLAG_COND) && wspop8()))
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(*ops[op])();
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dodevices();
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return 1;
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}
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int
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eval(void)
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{
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Uint8 instr = cpu.ram.dat[cpu.ram.ptr++];
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if(cpu.literal > 0)
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return doliteral(instr);
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else
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return doopcode(instr);
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return 1;
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}
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int
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load(FILE *f)
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{
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fread(cpu.ram.dat, sizeof(cpu.ram.dat), 1, f);
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return 1;
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}
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void
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echof(void)
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{
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printf("ended @ %d steps | hf: %x sf: %x sf: %x cf: %x\n",
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cpu.counter,
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getflag(FLAG_HALT) != 0,
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getflag(FLAG_SHORT) != 0,
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getflag(FLAG_SIGN) != 0,
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getflag(FLAG_COND) != 0);
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}
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int
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boot(void)
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{
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cpu.vreset = mempeek16(0xfffa);
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cpu.vframe = mempeek16(0xfffc);
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cpu.verror = mempeek16(0xfffe);
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/* eval reset */
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cpu.ram.ptr = cpu.vreset;
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setflag(FLAG_HALT, 0);
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while(!(cpu.status & FLAG_HALT) && eval())
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cpu.counter++;
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/*eval frame */
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cpu.ram.ptr = cpu.vframe;
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setflag(FLAG_HALT, 0);
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while(!(cpu.status & FLAG_HALT) && eval())
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cpu.counter++;
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return 1;
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}
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