ref: 899ec4d0b568a6d51a85e5344733a2189a7ba1ec
dir: /sys/src/games/2600/mem.c/
#include <u.h> #include <libc.h> #include "../eui.h" #include "dat.h" #include "fns.h" u8int ram[128], reg[64]; static u8int timer, timerun, timerspeed; static u16int timerpre; static u8int grp0d, grp1d, enabld; static u8int tiaread(u8int a) { if(a < 8) return coll >> (a << 1 & 14) << 6; if(a == 0xc) return ~keys << 3 & 0x80; return 0x80; } static void tiawrite(u8int a, u8int v) { switch(a){ case VSYNC: if((v & 2) != 0) flush(); return; case VBLANK: if((v & 2) == 0) ppuy = 0; break; case WSYNC: nrdy = 1; break; case RESP0: p0x = ppux >= 160 ? 3 : ppux+5; break; case RESP1: p1x = ppux >= 160 ? 3 : ppux+5; break; case RESM0: m0x = ppux >= 160 ? 2 : ppux+4; break; case RESM1: m1x = ppux >= 160 ? 2 : ppux+4; break; case RESBL: blx = ppux >= 160 ? 2 : ppux+4; break; case HMOVE: p0x = (p0x - ((s8int) reg[HMP0] >> 4)) % 160; p1x = (p1x - ((s8int) reg[HMP1] >> 4)) % 160; m0x = (m0x - ((s8int) reg[HMM0] >> 4)) % 160; m1x = (m1x - ((s8int) reg[HMM1] >> 4)) % 160; blx = (blx - ((s8int) reg[HMBL] >> 4)) % 160; break; case HMCLR: reg[HMP0] = reg[HMP1] = reg[HMM0] = reg[HMM1] = reg[HMBL] = 0; break; case VDELP0: if((v & 1) == 0) reg[GRP0] = grp0d; break; case VDELP1: if((v & 1) == 0) reg[GRP1] = grp1d; break; case VDELBL: if((v & 1) == 0) reg[ENABL] = enabld; break; case GRP0: if((reg[VDELP1] & 1) != 0) reg[GRP1] = grp1d; if((reg[VDELP0] & 1) != 0){ grp0d = v; return; } break; case GRP1: if((reg[VDELP0] & 1) != 0) reg[GRP0] = grp0d; if((reg[VDELBL] & 1) != 0) reg[ENABL] = enabld; if((reg[VDELP1] & 1) != 0){ grp1d = v; return; } break; case ENABL: if((reg[VDELBL] & 1) != 0){ enabld = v; return; } break; case CXCLR: coll = 0; break; } reg[a] = v; } static u8int ioread(u8int a) { u8int v; switch(a){ case 0: return ~(keys << 4); case 2: return keys >> 5 ^ 3 | bwmod | p0difc; case 4: timerspeed = 0; return timer; case 5: v = timerun; timerun &= ~(1<<6); return v; } return 0; } static void iowrite(u8int a, u8int v) { switch(a){ case 4: timerpre = 1; goto timer; case 5: timerpre = 8; goto timer; case 6: timerpre = 64; goto timer; case 7: timerpre = 1024; timer: timerun &= ~(1<<7); timerspeed = v == 0; timer = v - 1; break; } } u8int memread(u16int a) { u8int v; if((a & 0x1000) != 0) v = rop[a & mask]; else if((a & 1<<7) == 0) v = tiaread(a & 0xf); else if((a & 1<<9) == 0) v = ram[a & 0x7f]; else v = ioread(a & 7); if(a > 0xfff3 && a < 0xfffc) rop = rom + bnk[a - 0xfff4]; io(); return v; } void memwrite(u16int a, u8int v) { if((a & 0x1000) != 0){ ;} else if((a & 1<<7) == 0) tiawrite(a & 0x3f, v); else if((a & 1<<9) == 0) ram[a & 0x7f] = v; else iowrite(a & 7, v); if(a > 0xfff3 && a < 0xfffc) rop = rom + bnk[a - 0xfff4]; io(); } static void timerstep(void) { static int cl; cl++; if((timerspeed || (cl & timerpre - 1) == 0) && timer-- == 0){ timerspeed = 1; timerun |= 3<<6; } } void io(void) { static int snddiv; timerstep(); tiastep(); tiastep(); tiastep(); if(++snddiv == SAMPDIV){ snddiv = 0; sample(); } }