| /* altair_cpu.c: MITS Altair Intel 8080 CPU simulator | |
| Copyright (c) 1997, | |
| Charles E. Owen, Jr. | |
| Commercial use prohibited | |
| The register state for the 8080 CPU is: | |
| A<0:7> Accumulator | |
| BC<0:15> BC Register Pair | |
| DE<0:15> DE Register Pair | |
| HL<0:15> HL Register Pair | |
| C carry flag | |
| Z zero flag | |
| S Sign bit | |
| AC Aux carry | |
| P Parity bit | |
| PC<0:15> program counter | |
| SP<0:15> Stack Pointer | |
| The 8080 is an 8-bit CPU, which uses 16-bit registers to address | |
| up to 64KB of memory. | |
| The 78 basic instructions come in 1, 2, and 3-byte flavors. | |
| */ | |
| /* This routine is the instruction decode routine for the 8080. | |
| It is called from the simulator control program to execute | |
| instructions in simulated memory, starting at the simulated PC. | |
| It runs until 'reason' is set non-zero. | |
| General notes: | |
| 1. Reasons to stop. The simulator can be stopped by: | |
| HALT instruction | |
| I/O error in I/O simulator | |
| Invalid OP code (If ITRAP is set on CPU) | |
| 2. Interrupts. | |
| There are 8 possible levels of interrupt, and in effect they | |
| do a hardware CALL instruction to one of 8 possible low | |
| memory addresses. | |
| 3. Non-existent memory. On the 8080, reads to non-existent memory | |
| return 0377, and writes are ignored. In the simulator, the | |
| largest possible memory is instantiated and initialized to zero. | |
| Thus, only writes need be checked against actual memory size. | |
| 4. Adding I/O devices. These modules must be modified: | |
| altair_cpu.c add I/O service routines to dev_table | |
| altair_sys.c add pointer to data structures in sim_devices | |
| */ | |
| #include <stdio.h> | |
| #include "altair_defs.h" | |
| #define ILL_ADR_FLAG 0200000 | |
| #define save_ibkpt (cpu_unit.u3) | |
| #define UNIT_V_OPSTOP (UNIT_V_UF) /* Stop on Invalid OP? */ | |
| #define UNIT_OPSTOP (1 << UNIT_V_OPSTOP) | |
| #define UNIT_V_CHIP (UNIT_V_UF+1) /* 8080 or Z80 */ | |
| #define UNIT_CHIP (1 << UNIT_V_CHIP) | |
| #define UNIT_V_MSIZE (UNIT_V_UF+2) /* Memory Size */ | |
| #define UNIT_MSIZE (1 << UNIT_V_MSIZE) | |
| unsigned char M[MAXMEMSIZE]; /* memory */ | |
| int32 A = 0; /* accumulator */ | |
| int32 BC = 0; /* BC register pair */ | |
| int32 DE = 0; /* DE register pair */ | |
| int32 HL = 0; /* HL register pair */ | |
| int32 SP = 0; /* Stack pointer */ | |
| int32 C = 0; /* carry flag */ | |
| int32 Z = 0; /* Zero flag */ | |
| int32 AC = 0; /* Aux carry */ | |
| int32 S = 0; /* sign flag */ | |
| int32 P = 0; /* parity flag */ | |
| int32 saved_PC = 0; /* program counter */ | |
| int32 SR = 0; /* switch register */ | |
| int32 INTE = 0; /* Interrupt Enable */ | |
| int32 int_req = 0; /* Interrupt request */ | |
| int32 ibkpt_addr = ILL_ADR_FLAG | ADDRMASK; /* breakpoint addr */ | |
| int32 chip = 0; /* 0 = 8080 chip, 1 = z80 chip */ | |
| int32 PCX; /* External view of PC */ | |
| extern int32 sim_int_char; | |
| /* function prototypes */ | |
| t_stat cpu_ex (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw); | |
| t_stat cpu_dep (t_value val, t_addr addr, UNIT *uptr, int32 sw); | |
| t_stat cpu_reset (DEVICE *dptr); | |
| t_stat cpu_svc (UNIT *uptr); | |
| t_stat cpu_set_size (UNIT *uptr, int32 value); | |
| void setarith(int32 reg); | |
| void setlogical(int32 reg); | |
| void setinc(int32 reg); | |
| int32 getreg(int32 reg); | |
| void putreg(int32 reg, int32 val); | |
| int32 getpair(int32 reg); | |
| int32 getpush(int32 reg); | |
| void putpush(int32 reg, int32 data); | |
| void putpair(int32 reg, int32 val); | |
| void parity(int32 reg); | |
| int32 cond(int32 con); | |
| extern int32 sio0s(int32 io, int32 data); | |
| extern int32 sio0d(int32 io, int32 data); | |
| extern int32 sio1s(int32 io, int32 data); | |
| extern int32 sio1d(int32 io, int32 data); | |
| extern int32 dsk10(int32 io, int32 data); | |
| extern int32 dsk11(int32 io, int32 data); | |
| extern int32 dsk12(int32 io, int32 data); | |
| int32 nulldev(int32 io, int32 data); | |
| /* This is the I/O configuration table. There are 255 possible | |
| device addresses, if a device is plugged to a port it's routine | |
| address is here, 'nulldev' means no device is available | |
| */ | |
| struct idev { | |
| int32 (*routine)(); | |
| }; | |
| struct idev dev_table[256] = { | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 000 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 004 */ | |
| {&dsk10}, {&dsk11}, {&dsk12}, {&nulldev}, /* 010 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 014 */ | |
| {&sio0s}, {&sio0d}, {&sio1s}, {&sio1d}, /* 020 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 024 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 030 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 034 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 040 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 044 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 050 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 054 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 060 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 064 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 070 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 074 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 100 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 104 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 110 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 114 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 120 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 124 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 130 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 134 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 140 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 144 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 150 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 154 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 160 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 164 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 170 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 174 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 200 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 204 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 210 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 214 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 220 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 224 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 230 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 234 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 240 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 244 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 250 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 254 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 260 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 264 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 270 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 274 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 300 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 304 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 310 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 314 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 320 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 324 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 330 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 334 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 340 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 344 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 350 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 354 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 360 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 364 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev}, /* 370 */ | |
| {&nulldev}, {&nulldev}, {&nulldev}, {&nulldev} }; /* 374 */ | |
| /* Altair MITS standard BOOT EPROM, fits in upper 256K of memory */ | |
| int32 bootrom[256] = { | |
| 0041, 0000, 0114, 0021, 0030, 0377, 0016, 0346, | |
| 0032, 0167, 0023, 0043, 0015, 0302, 0010, 0377, | |
| 0303, 0000, 0114, 0000, 0000, 0000, 0000, 0000, | |
| 0363, 0061, 0142, 0115, 0257, 0323, 0010, 0076, /* 46000 */ | |
| 0004, 0323, 0011, 0303, 0031, 0114, 0333, 0010, /* 46010 */ | |
| 0346, 0002, 0302, 0016, 0114, 0076, 0002, 0323, /* 46020 */ | |
| 0011, 0333, 0010, 0346, 0100, 0302, 0016, 0114, | |
| 0021, 0000, 0000, 0006, 0000, 0333, 0010, 0346, | |
| 0004, 0302, 0045, 0114, 0076, 0020, 0365, 0325, | |
| 0305, 0325, 0021, 0206, 0200, 0041, 0324, 0114, | |
| 0333, 0011, 0037, 0332, 0070, 0114, 0346, 0037, | |
| 0270, 0302, 0070, 0114, 0333, 0010, 0267, 0372, | |
| 0104, 0114, 0333, 0012, 0167, 0043, 0035, 0312, | |
| 0132, 0114, 0035, 0333, 0012, 0167, 0043, 0302, | |
| 0104, 0114, 0341, 0021, 0327, 0114, 0001, 0200, | |
| 0000, 0032, 0167, 0276, 0302, 0301, 0114, 0200, | |
| 0107, 0023, 0043, 0015, 0302, 0141, 0114, 0032, | |
| 0376, 0377, 0302, 0170, 0114, 0023, 0032, 0270, | |
| 0301, 0353, 0302, 0265, 0114, 0361, 0361, 0052, | |
| 0325, 0114, 0325, 0021, 0000, 0377, 0315, 0316, | |
| 0114, 0321, 0332, 0276, 0114, 0315, 0316, 0114, | |
| 0322, 0256, 0114, 0004, 0004, 0170, 0376, 0040, | |
| 0332, 0054, 0114, 0006, 0001, 0312, 0054, 0114, | |
| 0333, 0010, 0346, 0002, 0302, 0240, 0114, 0076, | |
| 0001, 0323, 0011, 0303, 0043, 0114, 0076, 0200, | |
| 0323, 0010, 0303, 0000, 0000, 0321, 0361, 0075, | |
| 0302, 0056, 0114, 0076, 0103, 0001, 0076, 0117, | |
| 0001, 0076, 0115, 0107, 0076, 0200, 0323, 0010, | |
| 0170, 0323, 0001, 0303, 0311, 0114, 0172, 0274, | |
| 0300, 0173, 0275, 0311, 0204, 0000, 0114, 0044, | |
| 0026, 0126, 0026, 0000, 0000, 0000, 0000, 0000 | |
| }; | |
| /* CPU data structures | |
| cpu_dev CPU device descriptor | |
| cpu_unit CPU unit descriptor | |
| cpu_reg CPU register list | |
| cpu_mod CPU modifiers list | |
| */ | |
| UNIT cpu_unit = { UDATA (&cpu_svc, UNIT_FIX + UNIT_BINK, | |
| MAXMEMSIZE) }; | |
| REG cpu_reg[] = { | |
| { ORDATA (PC, saved_PC, 16) }, | |
| { ORDATA (A, A, 8) }, | |
| { ORDATA (BC, BC, 16) }, | |
| { ORDATA (DE, DE, 16) }, | |
| { ORDATA (HL, HL, 16) }, | |
| { ORDATA (SP, SP, 16) }, | |
| { FLDATA (C, C, 16) }, | |
| { FLDATA (Z, Z, 16) }, | |
| { FLDATA (AC, AC, 16) }, | |
| { FLDATA (S, S, 16) }, | |
| { FLDATA (P, P, 16) }, | |
| { FLDATA (INTE, INTE, 16) }, | |
| { FLDATA (Z80, cpu_unit.flags, UNIT_V_CHIP), REG_HRO }, | |
| { FLDATA (OPSTOP, cpu_unit.flags, UNIT_V_OPSTOP), REG_HRO }, | |
| { ORDATA (SR, SR, 16) }, | |
| { ORDATA (BREAK, ibkpt_addr, 17) }, | |
| { ORDATA (WRU, sim_int_char, 8) }, | |
| { NULL } }; | |
| MTAB cpu_mod[] = { | |
| { UNIT_CHIP, UNIT_CHIP, "Z80", "Z80", NULL }, | |
| { UNIT_CHIP, 0, "8080", "8080", NULL }, | |
| { UNIT_OPSTOP, UNIT_OPSTOP, "ITRAP", "ITRAP", NULL }, | |
| { UNIT_OPSTOP, 0, "NOITRAP", "NOITRAP", NULL }, | |
| { UNIT_MSIZE, 4096, NULL, "4K", &cpu_set_size }, | |
| { UNIT_MSIZE, 8192, NULL, "8K", &cpu_set_size }, | |
| { UNIT_MSIZE, 12288, NULL, "12K", &cpu_set_size }, | |
| { UNIT_MSIZE, 16384, NULL, "16K", &cpu_set_size }, | |
| { UNIT_MSIZE, 20480, NULL, "20K", &cpu_set_size }, | |
| { UNIT_MSIZE, 24576, NULL, "24K", &cpu_set_size }, | |
| { UNIT_MSIZE, 28672, NULL, "28K", &cpu_set_size }, | |
| { UNIT_MSIZE, 32768, NULL, "32K", &cpu_set_size }, | |
| { UNIT_MSIZE, 49152, NULL, "48K", &cpu_set_size }, | |
| { UNIT_MSIZE, 65535, NULL, "64K", &cpu_set_size }, | |
| { 0 } }; | |
| DEVICE cpu_dev = { | |
| "CPU", &cpu_unit, cpu_reg, cpu_mod, | |
| 1, 8, 16, 1, 8, 8, | |
| &cpu_ex, &cpu_dep, &cpu_reset, | |
| NULL, NULL, NULL }; | |
| int32 sim_instr (void) | |
| { | |
| extern int32 sim_interval; | |
| int32 PC, IR, OP, DAR, reason, hi, lo, carry, i; | |
| PC = saved_PC & ADDRMASK; /* load local PC */ | |
| C = C & 0200000; | |
| reason = 0; | |
| /* Main instruction fetch/decode loop */ | |
| while (reason == 0) { /* loop until halted */ | |
| if (sim_interval <= 0) { /* check clock queue */ | |
| if (reason = sim_process_event ()) break; | |
| } | |
| if (int_req > 0) { /* interrupt? */ | |
| /* 8080 interrupts not implemented yet. None were used, | |
| on a standard Altair 8800. All I/O is programmed. */ | |
| } /* end interrupt */ | |
| if (PC == ibkpt_addr) { /* breakpoint? */ | |
| save_ibkpt = ibkpt_addr; /* save address */ | |
| ibkpt_addr = ibkpt_addr | ILL_ADR_FLAG; /* disable */ | |
| sim_activate (&cpu_unit, 1); /* sched re-enable */ | |
| reason = STOP_IBKPT; /* stop simulation */ | |
| break; | |
| } | |
| if (PC == 0177400) { /* BOOT PROM address */ | |
| for (i = 0; i < 250; i++) { | |
| M[i + 0177400] = bootrom[i] & 0xFF; | |
| } | |
| } | |
| PCX = PC; | |
| IR = OP = M[PC]; /* fetch instruction */ | |
| PC = (PC + 1) & ADDRMASK; /* increment PC */ | |
| sim_interval--; | |
| if (OP == 0166) { /* HLT Instruction*/ | |
| reason = STOP_HALT; | |
| PC--; | |
| continue; | |
| } | |
| /* Handle below all operations which refer to registers or | |
| register pairs. After that, a large switch statement | |
| takes care of all other opcodes */ | |
| if ((OP & 0xC0) == 0x40) { /* MOV */ | |
| DAR = getreg(OP & 0x07); | |
| putreg((OP >> 3) & 0x07, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0x06) { /* MVI */ | |
| putreg((OP >> 3) & 0x07, M[PC]); | |
| PC++; | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0x01) { /* LXI */ | |
| DAR = M[PC] & 0x00ff; | |
| PC++; | |
| DAR = DAR | (M[PC] <<8) & 0xFF00;; | |
| putpair((OP >> 4) & 0x03, DAR); | |
| PC++; | |
| continue; | |
| } | |
| if ((OP & 0xEF) == 0x0A) { /* LDAX */ | |
| DAR = getpair((OP >> 4) & 0x03); | |
| putreg(7, M[DAR]); | |
| continue; | |
| } | |
| if ((OP & 0xEF) == 0x02) { /* STAX */ | |
| DAR = getpair((OP >> 4) & 0x03); | |
| M[DAR] = getreg(7); | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0xB8) { /* CMP */ | |
| DAR = A & 0xFF; | |
| DAR -= getreg(OP & 0x07); | |
| setarith(DAR); | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0xC2) { /* JMP <condition> */ | |
| if (cond((OP >> 3) & 0x07) == 1) { | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| PC = (hi << 8) + lo; | |
| } else { | |
| PC += 2; | |
| } | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0xC4) { /* CALL <condition> */ | |
| if (cond((OP >> 3) & 0x07) == 1) { | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| SP--; | |
| M[SP] = (PC >> 8) & 0xff; | |
| SP--; | |
| M[SP] = PC & 0xff; | |
| PC = (hi << 8) + lo; | |
| } else { | |
| PC += 2; | |
| } | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0xC0) { /* RET <condition> */ | |
| if (cond((OP >> 3) & 0x07) == 1) { | |
| PC = M[SP]; | |
| SP++; | |
| PC |= (M[SP] << 8) & 0xff00; | |
| SP++; | |
| } | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0xC7) { /* RST */ | |
| SP--; | |
| M[SP] = (PC >> 8) & 0xff; | |
| SP--; | |
| M[SP] = PC & 0xff; | |
| PC = OP & 0x38; | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0xC5) { /* PUSH */ | |
| DAR = getpush((OP >> 4) & 0x03); | |
| SP--; | |
| M[SP] = (DAR >> 8) & 0xff; | |
| SP--; | |
| M[SP] = DAR & 0xff; | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0xC1) { /*POP */ | |
| DAR = M[SP]; | |
| SP++; | |
| DAR |= M[SP] << 8; | |
| SP++; | |
| putpush((OP >> 4) & 0x03, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0x80) { /* ADD */ | |
| A += getreg(OP & 0x07); | |
| setarith(A); | |
| A = A & 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0x88) { /* ADC */ | |
| carry = 0; | |
| if (C) carry = 1; | |
| A += getreg(OP & 0x07); | |
| A += carry; | |
| setarith(A); | |
| A = A & 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0x90) { /* SUB */ | |
| A -= getreg(OP & 0x07); | |
| setarith(A); | |
| A = A & 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0x98) { /* SBB */ | |
| carry = 0; | |
| if (C) carry = 1; | |
| A -= (getreg(OP & 0x07)) + carry ; | |
| setarith(A); | |
| A = A & 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0x04) { /* INR */ | |
| DAR = getreg((OP >> 3) & 0x07); | |
| DAR++; | |
| setinc(DAR); | |
| DAR = DAR & 0xFF; | |
| putreg((OP >> 3) & 0x07, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xC7) == 0x05) { /* DCR */ | |
| DAR = getreg((OP >> 3) & 0x07); | |
| DAR--; | |
| setinc(DAR); | |
| DAR = DAR & 0xFF; | |
| putreg((OP >> 3) & 0x07, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0x03) { /* INX */ | |
| DAR = getpair((OP >> 4) & 0x03); | |
| DAR++; | |
| DAR = DAR & 0xFFFF; | |
| putpair((OP >> 4) & 0x03, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0x0B) { /* DCX */ | |
| DAR = getpair((OP >> 4) & 0x03); | |
| DAR--; | |
| DAR = DAR & 0xFFFF; | |
| putpair((OP >> 4) & 0x03, DAR); | |
| continue; | |
| } | |
| if ((OP & 0xCF) == 0x09) { /* DAD */ | |
| HL += getpair((OP >> 4) & 0x03); | |
| C = 0; | |
| if (HL & 0x10000) | |
| C = 0200000; | |
| HL = HL & 0xFFFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0xA0) { /* ANA */ | |
| A &= getreg(OP & 0x07); | |
| C = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0xA8) { /* XRA */ | |
| A ^= getreg(OP & 0x07); | |
| C = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| continue; | |
| } | |
| if ((OP & 0xF8) == 0xB0) { /* ORA */ | |
| A |= getreg(OP & 0x07); | |
| C = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| continue; | |
| } | |
| /* The Big Instruction Decode Switch */ | |
| switch (IR) { | |
| /* Logical instructions */ | |
| case 0376: { /* CPI */ | |
| DAR = A & 0xFF; | |
| DAR -= M[PC]; | |
| PC++; | |
| setarith(DAR); | |
| break; | |
| } | |
| case 0346: { /* ANI */ | |
| A &= M[PC]; | |
| PC++; | |
| C = AC = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| break; | |
| } | |
| case 0356: { /* XRI */ | |
| A ^= M[PC]; | |
| PC++; | |
| C = AC = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| break; | |
| } | |
| case 0366: { /* ORI */ | |
| A |= M[PC]; | |
| PC++; | |
| C = AC = 0; | |
| setlogical(A); | |
| A &= 0xFF; | |
| break; | |
| } | |
| /* Jump instructions */ | |
| case 0303: { /* JMP */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| PC = (hi << 8) + lo; | |
| break; | |
| } | |
| case 0351: { /* PCHL */ | |
| PC = HL; | |
| break; | |
| } | |
| case 0315: { /* CALL */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| SP--; | |
| M[SP] = (PC >> 8) & 0xff; | |
| SP--; | |
| M[SP] = PC & 0xff; | |
| PC = (hi << 8) + lo; | |
| break; | |
| } | |
| case 0311: { /* RET */ | |
| PC = M[SP]; | |
| SP++; | |
| PC |= (M[SP] << 8) & 0xff00; | |
| SP++; | |
| break; | |
| } | |
| /* Data Transfer Group */ | |
| case 062: { /* STA */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| DAR = (hi << 8) + lo; | |
| M[DAR] = A; | |
| break; | |
| } | |
| case 072: { /* LDA */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| DAR = (hi << 8) + lo; | |
| A = M[DAR]; | |
| break; | |
| } | |
| case 042: { /* SHLD */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| DAR = (hi << 8) + lo; | |
| M[DAR] = HL; | |
| DAR++; | |
| M[DAR] = (HL >>8) & 0x00ff; | |
| break; | |
| } | |
| case 052: { /* LHLD */ | |
| lo = M[PC]; | |
| PC++; | |
| hi = M[PC]; | |
| PC++; | |
| DAR = (hi << 8) + lo; | |
| HL = M[DAR]; | |
| DAR++; | |
| HL = HL | (M[DAR] <<8); | |
| break; | |
| } | |
| case 0353: { /* XCHG */ | |
| DAR = HL; | |
| HL = DE; | |
| DE = DAR; | |
| break; | |
| } | |
| /* Arithmetic Group */ | |
| case 0306: { /* ADI */ | |
| A += M[PC]; | |
| PC++; | |
| setarith(A); | |
| A = A & 0xFF; | |
| break; | |
| } | |
| case 0316: { /* ACI */ | |
| carry = 0; | |
| if (C) carry = 1; | |
| A += M[PC]; | |
| A += carry; | |
| PC++; | |
| setarith(A); | |
| A = A & 0xFF; | |
| break; | |
| } | |
| case 0326: { /* SUI */ | |
| A -= M[PC]; | |
| PC++; | |
| setarith(A); | |
| A = A & 0xFF; | |
| break; | |
| } | |
| case 0336: { /* SBI */ | |
| carry = 0; | |
| if (C) carry = 1; | |
| A -= (M[PC] + carry); | |
| PC++; | |
| setarith(A); | |
| A = A & 0xFF; | |
| break; | |
| } | |
| case 047: { /* DAA */ | |
| DAR = A & 0x0F; | |
| if (DAR > 9 || AC > 0) { | |
| DAR += 6; | |
| A &= 0xF0; | |
| A |= DAR & 0x0F; | |
| if (DAR & 0x10) | |
| AC = 0200000; | |
| else | |
| AC = 0; | |
| } | |
| DAR = (A >> 4) & 0x0F; | |
| if (DAR > 9 || AC > 0) { | |
| DAR += 6; | |
| if (AC) DAR++; | |
| A &= 0x0F; | |
| A |= (DAR << 4); | |
| } | |
| if ((DAR << 4) & 0x100) | |
| C = 0200000; | |
| else | |
| C = 0; | |
| if (A & 0x80) { | |
| S = 0200000; | |
| } else { | |
| S = 0; | |
| } | |
| if ((A & 0xff) == 0) | |
| Z = 0200000; | |
| else | |
| Z = 0; | |
| parity(A); | |
| A = A & 0xFF; | |
| break; | |
| } | |
| case 07: { /* RLC */ | |
| C = 0; | |
| C = (A << 9) & 0200000; | |
| A = (A << 1) & 0xFF; | |
| if (C) | |
| A |= 0x01; | |
| break; | |
| } | |
| case 017: { /* RRC */ | |
| C = 0; | |
| if (A & 0x01 == 1) | |
| C |= 0200000; | |
| A = (A >> 1) & 0xFF; | |
| if (C) | |
| A |= 0x80; | |
| break; | |
| } | |
| case 027: { /* RAL */ | |
| DAR = C; | |
| C = 0; | |
| C = (A << 9) & 0200000; | |
| A = (A << 1) & 0xFF; | |
| if (DAR) | |
| A |= 1; | |
| else | |
| A &= 0xFE; | |
| break; | |
| } | |
| case 037: { /* RAR */ | |
| DAR = C; | |
| C = 0; | |
| if (A & 0x01 == 1) | |
| C |= 0200000; | |
| A = (A >> 1) & 0xFF; | |
| if (DAR) | |
| A |= 0x80; | |
| else | |
| A &= 0x7F; | |
| break; | |
| } | |
| case 057: { /* CMA */ | |
| A = ~ A; | |
| A &= 0xFF; | |
| break; | |
| } | |
| case 077: { /* CMC */ | |
| C = ~ C; | |
| C &= 0200000; | |
| break; | |
| } | |
| case 067: { /* STC */ | |
| C = 0200000; | |
| break; | |
| } | |
| /* Stack, I/O & Machine Control Group */ | |
| case 0: { /* NOP */ | |
| break; | |
| } | |
| case 0343: { /* XTHL */ | |
| lo = M[SP]; | |
| hi = M[SP + 1]; | |
| M[SP] = HL & 0xFF; | |
| M[SP + 1] = (HL >> 8) & 0xFF; | |
| HL = (hi << 8) + lo; | |
| break; | |
| } | |
| case 0371: { /* SPHL */ | |
| SP = HL; | |
| break; | |
| } | |
| case 0373: { /* EI */ | |
| INTE = 0200000; | |
| break; | |
| } | |
| case 0363: { /* DI */ | |
| INTE = 0; | |
| break; | |
| } | |
| case 0333: { /* IN */ | |
| DAR = M[PC] & 0xFF; | |
| PC++; | |
| if (DAR == 0xFF) { | |
| A = (SR >> 8) & 0xFF; | |
| } else { | |
| A = dev_table[DAR].routine(0, 0); | |
| } | |
| break; | |
| } | |
| case 0323: { /* OUT */ | |
| DAR = M[PC] & 0xFF; | |
| PC++; | |
| dev_table[DAR].routine(1, A); | |
| break; | |
| } | |
| default: { | |
| if (cpu_unit.flags & UNIT_OPSTOP) { | |
| reason = STOP_OPCODE; | |
| PC--; | |
| } | |
| break; | |
| } | |
| } | |
| } | |
| /* Simulation halted */ | |
| saved_PC = PC; | |
| return reason; | |
| } | |
| /* Test an 8080 flag condition and return 1 if true, 0 if false */ | |
| int32 cond(int32 con) | |
| { | |
| int32 r = 0; | |
| switch (con) { | |
| case 0: | |
| if (Z == 0) return (1); | |
| break; | |
| case 1: | |
| if (Z != 0) return (1); | |
| break; | |
| case 2: | |
| if (C == 0) return (1); | |
| break; | |
| case 3: | |
| if (C != 0) return (1); | |
| break; | |
| case 4: | |
| if (P == 0) return (1); | |
| break; | |
| case 5: | |
| if (P != 0) return (1); | |
| break; | |
| case 6: | |
| if (S == 0) return (1); | |
| break; | |
| case 7: | |
| if (S != 0) return (1); | |
| break; | |
| default: | |
| break; | |
| } | |
| return (0); | |
| } | |
| /* Set the <C>arry, <S>ign, <Z>ero and <P>arity flags following | |
| an arithmetic operation on 'reg'. | |
| */ | |
| void setarith(int32 reg) | |
| { | |
| int32 bc = 0; | |
| if (reg & 0x100) | |
| C = 0200000; | |
| else | |
| C = 0; | |
| if (reg & 0x80) { | |
| bc++; | |
| S = 0200000; | |
| } else { | |
| S = 0; | |
| } | |
| if ((reg & 0xff) == 0) | |
| Z = 0200000; | |
| else | |
| Z = 0; | |
| AC = 0; | |
| if (cpu_unit.flags & UNIT_CHIP) { | |
| P = 0; /* parity is zero for *all* arith ops on Z80 */ | |
| } else { | |
| parity(reg); | |
| } | |
| } | |
| /* Set the <C>arry, <S>ign, <Z>ero amd <P>arity flags following | |
| a logical (bitwise) operation on 'reg'. | |
| */ | |
| void setlogical(int32 reg) | |
| { | |
| C = 0; | |
| if (reg & 0x80) { | |
| S = 0200000; | |
| } else { | |
| S = 0; | |
| } | |
| if ((reg & 0xff) == 0) | |
| Z = 0200000; | |
| else | |
| Z = 0; | |
| AC = 0; | |
| parity(reg); | |
| } | |
| /* Set the Parity (P) flag based on parity of 'reg', i.e., number | |
| of bits on even: P=0200000, else P=0 | |
| */ | |
| void parity(int32 reg) | |
| { | |
| int32 bc = 0; | |
| if (reg & 0x01) bc++; | |
| if (reg & 0x02) bc++; | |
| if (reg & 0x04) bc++; | |
| if (reg & 0x08) bc++; | |
| if (reg & 0x10) bc++; | |
| if (reg & 0x20) bc++; | |
| if (reg & 0x40) bc++; | |
| if (reg & 0x80) bc++; | |
| P = ~(bc << 16); | |
| P &= 0200000; | |
| } | |
| /* Set the <S>ign, <Z>ero amd <P>arity flags following | |
| an INR/DCR operation on 'reg'. | |
| */ | |
| void setinc(int32 reg) | |
| { | |
| int32 bc = 0; | |
| if (reg & 0x80) { | |
| bc++; | |
| S = 0200000; | |
| } else { | |
| S = 0; | |
| } | |
| if ((reg & 0xff) == 0) | |
| Z = 0200000; | |
| else | |
| Z = 0; | |
| if (cpu_unit.flags & UNIT_CHIP) { | |
| P = 0; /* parity is zero for *all* arith ops on Z80 */ | |
| } else { | |
| parity(reg); | |
| } | |
| } | |
| /* Get an 8080 register and return it */ | |
| int32 getreg(int32 reg) | |
| { | |
| switch (reg) { | |
| case 0: | |
| return ((BC >>8) & 0x00ff); | |
| case 1: | |
| return (BC & 0x00FF); | |
| case 2: | |
| return ((DE >>8) & 0x00ff); | |
| case 3: | |
| return (DE & 0x00ff); | |
| case 4: | |
| return ((HL >>8) & 0x00ff); | |
| case 5: | |
| return (HL & 0x00ff); | |
| case 6: | |
| return (M[HL]); | |
| case 7: | |
| return (A); | |
| default: | |
| break; | |
| } | |
| } | |
| /* Put a value into an 8080 register from memory */ | |
| void putreg(int32 reg, int32 val) | |
| { | |
| switch (reg) { | |
| case 0: | |
| BC = BC & 0x00FF; | |
| BC = BC | (val <<8); | |
| break; | |
| case 1: | |
| BC = BC & 0xFF00; | |
| BC = BC | val; | |
| break; | |
| case 2: | |
| DE = DE & 0x00FF; | |
| DE = DE | (val <<8); | |
| break; | |
| case 3: | |
| DE = DE & 0xFF00; | |
| DE = DE | val; | |
| break; | |
| case 4: | |
| HL = HL & 0x00FF; | |
| HL = HL | (val <<8); | |
| break; | |
| case 5: | |
| HL = HL & 0xFF00; | |
| HL = HL | val; | |
| break; | |
| case 6: | |
| M[HL] = val & 0xff; | |
| break; | |
| case 7: | |
| A = val & 0xff; | |
| default: | |
| break; | |
| } | |
| } | |
| /* Return the value of a selected register pair */ | |
| int32 getpair(int32 reg) | |
| { | |
| switch (reg) { | |
| case 0: | |
| return (BC); | |
| case 1: | |
| return (DE); | |
| case 2: | |
| return (HL); | |
| case 3: | |
| return (SP); | |
| default: | |
| break; | |
| } | |
| } | |
| /* Return the value of a selected register pair, in PUSH | |
| format where 3 means A& flags, not SP */ | |
| int32 getpush(int32 reg) | |
| { | |
| int32 stat; | |
| switch (reg) { | |
| case 0: | |
| return (BC); | |
| case 1: | |
| return (DE); | |
| case 2: | |
| return (HL); | |
| case 3: | |
| stat = A << 8; | |
| if (S) stat |= 0x80; | |
| if (Z) stat |= 0x40; | |
| if (AC) stat |= 0x10; | |
| if (P) stat |= 0x04; | |
| stat |= 0x02; | |
| if (C) stat |= 0x01; | |
| return (stat); | |
| default: | |
| break; | |
| } | |
| } | |
| /* Place data into the indicated register pair, in PUSH | |
| format where 3 means A& flags, not SP */ | |
| void putpush(int32 reg, int32 data) | |
| { | |
| switch (reg) { | |
| case 0: | |
| BC = data; | |
| break; | |
| case 1: | |
| DE = data; | |
| break; | |
| case 2: | |
| HL = data; | |
| break; | |
| case 3: | |
| A = (data >> 8) & 0xff; | |
| S = Z = AC = P = C = 0; | |
| if (data & 0x80) S = 0200000; | |
| if (data & 0x40) Z = 0200000; | |
| if (data & 0x10) AC = 0200000; | |
| if (data & 0x04) P = 0200000; | |
| if (data & 0x01) C = 0200000; | |
| break; | |
| default: | |
| break; | |
| } | |
| } | |
| /* Put a value into an 8080 register pair */ | |
| void putpair(int32 reg, int32 val) | |
| { | |
| switch (reg) { | |
| case 0: | |
| BC = val; | |
| break; | |
| case 1: | |
| DE = val; | |
| break; | |
| case 2: | |
| HL = val; | |
| break; | |
| case 3: | |
| SP = val; | |
| break; | |
| default: | |
| break; | |
| } | |
| } | |
| /* Reset routine */ | |
| t_stat cpu_reset (DEVICE *dptr) | |
| { | |
| C = 0; | |
| Z = 0; | |
| saved_PC = 0; | |
| int_req = 0; | |
| return cpu_svc (&cpu_unit); | |
| } | |
| /* Memory examine */ | |
| t_stat cpu_ex (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw) | |
| { | |
| if (addr >= MEMSIZE) return SCPE_NXM; | |
| if (vptr != NULL) *vptr = M[addr] & 0377; | |
| return SCPE_OK; | |
| } | |
| /* Memory deposit */ | |
| t_stat cpu_dep (t_value val, t_addr addr, UNIT *uptr, int32 sw) | |
| { | |
| if (addr >= MEMSIZE) return SCPE_NXM; | |
| M[addr] = val & 0377; | |
| return SCPE_OK; | |
| } | |
| /* Breakpoint service */ | |
| t_stat cpu_svc (UNIT *uptr) | |
| { | |
| if ((ibkpt_addr & ~ILL_ADR_FLAG) == save_ibkpt) | |
| ibkpt_addr = save_ibkpt; | |
| save_ibkpt = -1; | |
| return SCPE_OK; | |
| } | |
| t_stat cpu_set_size (UNIT *uptr, int32 value) | |
| { | |
| int32 mc = 0; | |
| t_addr i; | |
| if ((value <= 0) || (value > MAXMEMSIZE) || ((value & 07777) != 0)) | |
| return SCPE_ARG; | |
| for (i = value; i < MEMSIZE; i++) mc = mc | M[i]; | |
| if ((mc != 0) && (!get_yn ("Really truncate memory [N]?", FALSE))) | |
| return SCPE_OK; | |
| MEMSIZE = value; | |
| for (i = MEMSIZE; i < MAXMEMSIZE; i++) M[i] = 0; | |
| return SCPE_OK; | |
| } | |
| int32 nulldev(int32 flag, int32 data) | |
| { | |
| if (flag == 0) | |
| return (0377); | |
| } | |