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◆ riscv-1 x16-emulator / src / cpu / modes.h
6.7 KiB · Objective-C · last changed chore(): initial commit 15 days ago source blame history raw
03a3459e Andy McCall 1 
/*
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						Extracted from original single fake6502.c file
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*/
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//
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//          65C02 changes.
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//
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//          ind         absolute indirect
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//
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//                      A 6502 has a bug whereby if you jmp ($12FF) it reads the address from
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//                      $12FF and $1200. This has been fixed in the 65C02.
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//
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static void imp() { //implied
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}
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static void imp8() { // brk / cop
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}
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static void acc() { //accumulator
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}
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static void imm8() { //immediate, 8bit
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    ea = regs.pc++;
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}
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static void immm() { //immediate, 16bit if M = 0
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    ea = regs.pc++;
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    if (memory_16bit()) {
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        regs.pc++;
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    }
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}
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static void immx() { //immediate, 16bit if M = 0
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    ea = regs.pc++;
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    if (index_16bit()) {
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        regs.pc++;
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    }
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}
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static void imm16() {
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    ea = regs.pc;
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    regs.pc += 2;
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}
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static void _zp_with_offset(uint16_t offset) {
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    uint16_t imm_value = (uint16_t) read6502((uint16_t)regs.pc++, regs.k);
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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    ea = direct_page_add(imm_value + offset);
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}
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static void _zp_long_with_offset(uint16_t offset) {
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    uint16_t eahelp;
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    eahelp = (uint16_t)read6502(regs.pc++, regs.k);
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    ea = (uint16_t)read6502(regs.dp + eahelp, regs.k) | ((uint16_t)read6502(regs.dp + eahelp + 1, regs.k) << 8) | ((uint16_t)read6502(regs.dp + eahelp + 2, regs.k) << 16);
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    ea = mask_long_addr(ea + offset);
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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}
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static void zp() { //zero-page
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    _zp_with_offset(0);
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}
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static void zpx() { //zero-page,X
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    _zp_with_offset(regs.x);
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}
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static void zpy() { //zero-page,Y
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    _zp_with_offset(regs.y);
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}
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static void rel() { //relative for branch ops (8-bit immediate value, sign-extended)
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    reladdr = (uint16_t)read6502(regs.pc++, regs.k);
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    if (reladdr & 0x80) reladdr |= 0xFF00;
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}
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static void rel16() { //relative for PER and BRL (16-bit immediate value)
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    reladdr = (uint16_t)read6502(regs.pc, regs.k) | ((uint16_t)read6502(regs.pc+1, regs.k) << 8);
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    regs.pc += 2;
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}
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static void abso() { //absolute
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    ea = addr_with_db((uint16_t) read6502(regs.pc, regs.k) | ((uint16_t)read6502(regs.pc+1, regs.k) << 8));
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    regs.pc += 2;
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}
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static void absl() { // absolute long
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    ea = (uint32_t) read6502(regs.pc, regs.k) | ((uint32_t)read6502(regs.pc+1, regs.k) << 8) | ((uint32_t)read6502(regs.pc+2, regs.k) << 16);
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    regs.pc += 3;
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}
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static void absx() { //absolute,X
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    uint16_t startpage;
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    ea = addr_with_db((uint16_t)read6502(regs.pc, regs.k) | ((uint16_t)read6502(regs.pc+1, regs.k) << 8));
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    startpage = ea & 0xFF00;
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    ea = mask_long_addr(ea + regs.x);
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    if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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        penaltyaddr = 1;
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    }
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    regs.pc += 2;
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}
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static void abslx() { // absolute long, X
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    uint16_t startpage;
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    ea = (uint32_t)read6502(regs.pc, regs.k) | ((uint32_t)read6502(regs.pc+1, regs.k) << 8) | ((uint32_t)read6502(regs.pc+2, regs.k) << 16);
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    startpage = ea & 0xFF00;
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    ea = mask_long_addr(ea + regs.x);
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    if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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        penaltyaddr = 1;
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    }
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    regs.pc += 3;
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}
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static void absy() { //absolute,Y
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    uint16_t startpage;
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    ea = addr_with_db((uint16_t)read6502(regs.pc, regs.k) | ((uint16_t)read6502(regs.pc+1, regs.k) << 8));
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    startpage = ea & 0xFF00;
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    ea = mask_long_addr(ea + regs.y);
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    if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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        penaltyaddr = 1;
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    }
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    regs.pc += 2;
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}
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static void ind() { //indirect - used for jmp, which assumes the pointer is in bank 0!
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    uint16_t eahelp, eahelp2;
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    eahelp = (uint16_t)read6502(regs.pc, regs.k) | (uint16_t)((uint16_t)read6502(regs.pc+1, regs.k) << 8);
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    //
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    //      The 6502 page boundary wraparound bug does not occur on a 65C02.
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    //
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    //eahelp2 = (eahelp & 0xFF00) | ((eahelp + 1) & 0x00FF); //replicate 6502 page-boundary wraparound bug
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    eahelp2 = (eahelp+1) & 0xFFFF;
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    ea = (uint16_t)read6502(eahelp, 0) | ((uint16_t)read6502(eahelp2, 0) << 8);
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    regs.pc += 2;
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}
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static void aindl() { // [addr]    uint16_t eahelp, eahelp2;
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    uint16_t eahelp, eahelp2;
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    eahelp = (uint16_t)read6502(regs.pc, regs.k) | (uint16_t)((uint16_t)read6502(regs.pc+1, regs.k) << 8);
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    eahelp2 = (eahelp+1) & 0xFFFF;
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    ea = (uint32_t)read6502(eahelp, 0) | ((uint32_t)read6502(eahelp2, 0) << 8) | ((uint16_t)read6502((eahelp2 + 1) & 0xFFFF, 0) << 16);
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    regs.pc += 2;
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}
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static void ind0() { // (zp)
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    uint16_t eahelp;
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    eahelp = (uint16_t)read6502(regs.pc++, regs.k);
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    ea = (uint16_t)read6502(direct_page_add(eahelp), 0) | ((uint16_t)read6502(direct_page_add(eahelp + 1), 0) << 8);
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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}
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static void indl0() { // [dp]
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    _zp_long_with_offset(0);
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}
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static void indx() { // (indirect,X)
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    uint16_t eahelp;
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    eahelp = (uint16_t)read6502(regs.pc++, regs.k) + regs.x;
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    ea = (uint16_t)read6502(direct_page_add(eahelp), 0) | ((uint16_t)read6502(direct_page_add(eahelp + 1), 0) << 8);
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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}
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static void indy() { // (indirect),Y
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    uint16_t eahelp, startpage;
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    eahelp = (uint16_t)read6502(regs.pc++, regs.k);
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    ea = (uint16_t)read6502(direct_page_add(eahelp), 0) | ((uint16_t)read6502(direct_page_add(eahelp + 1), 0) << 8);
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    startpage = ea & 0xFF00;
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    ea += regs.y;
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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    if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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        penaltyaddr = 1;
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    }
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}
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static void indly() { // [dp],Y
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    _zp_long_with_offset(regs.y);
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}
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static void ind0p() { // (zp) used by PEI, which doesn't do wraparound calculations
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    uint16_t eahelp;
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    eahelp = (uint16_t)read6502(regs.pc++, regs.k);
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    ea = (uint16_t)read6502(regs.dp + eahelp, 0) | ((uint16_t)read6502(regs.dp + eahelp + 1, 0) << 8);
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    if (regs.dp & 0x00FF) {
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        penaltyd = 1;
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    }
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}
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static void zprel() { // zero-page, relative for branch ops (8-bit immediatel value, sign-extended) - only used for the 65C02's Rockwell extensions
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	ea = (uint16_t)read6502(regs.pc, 0);
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	reladdr = (uint16_t)read6502(regs.pc+1, 0);
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	if (reladdr & 0x80) reladdr |= 0xFF00;
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	regs.pc += 2;
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}
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static void sr() { // absolute,S
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    ea = regs.sp + (uint16_t)read6502(regs.pc++, regs.k);
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}
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static void sridy() { // (indirect,S),Y
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    uint16_t eahelp, startpage;
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    eahelp = regs.sp + (uint16_t)read6502(regs.pc++, regs.k);
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    ea = (uint16_t)read6502(eahelp, 0) | ((uint16_t)read6502(eahelp + 1, 0) << 8);
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    startpage = ea & 0xFF00;
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    ea += (uint16_t)regs.y;
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    if (startpage != (ea & 0xFF00)) { //one cycle penlty for page-crossing on some opcodes
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        penaltyaddr = 1;
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    }
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}
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static void bmv() { // block move
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    uint8_t dest = read6502(regs.pc++, regs.k);
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    ea = (read6502(regs.pc++, regs.k) << 8) | dest;
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}