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408 lines
12 KiB
C
408 lines
12 KiB
C
/*=====================================================================
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z80.c -> Main File related to the Z80 emulation code.
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Please read documentation files to know how this works :)
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Thanks go to Marat Fayzullin (read z80.h for more info), Raúl Gomez
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(check his great R80 Spectrum emulator!), Philip Kendall (some code
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of this emulator, such as the flags lookup tabled are from his fuse
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Spectrum emulator) and more people I forget to name here ...
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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Copyright (c) 2000 Santiago Romero Iglesias.
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Email: sromero@escomposlinux.org
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======================================================================*/
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#include "z80.h"
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#include "tables.h"
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/* RAM variable, debug toggle variable, pressed key and
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row variables for keyboard emulation */
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extern byte *RAM;
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extern int debug, main_tecla, scanl;
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extern int fila[5][5];
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//extern char *tapfile;
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//extern FILE *tapfile;
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extern char *tfont;
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#include "macros.c"
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/*====================================================================
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void Z80Reset( Z80Regs *regs, int cycles )
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This function simulates a z80 reset by setting the registers
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to the values they are supposed to take on a real z80 reset.
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You must pass it the Z80 register structure and the number
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of cycles required to check for interrupts and do special
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hardware checking/updating.
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===================================================================*/
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void Z80Reset( Z80Regs *regs, int int_cycles )
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{
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/* reset PC and the rest of main registers: */
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regs->PC.W = regs->R.W = 0x0000;
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regs->AF.W = regs->BC.W = regs->DE.W = regs->HL.W =
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regs->AFs.W = regs->BCs.W = regs->DEs.W = regs->HLs.W =
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regs->IX.W = regs->IY.W = 0x0000;
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/* Make the stack point to $F000 */
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regs->SP.W = 0xF000;
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/* reset variables to their default values */
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regs->I = 0x00;
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regs->IFF1 = regs->IFF2 = regs->IM = regs->halted = 0x00;
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regs->ICount = regs->IPeriod = int_cycles;
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regs->IRequest = INT_NOINT;
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regs->we_are_on_ddfd = regs->dobreak = regs->BorderColor = 0;
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//#ifdef _DEBUG_
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regs->DecodingErrors = 1;
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//#endif
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}
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/*====================================================================
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word Z80Run( Z80Regs *regs, int numopcodes )
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This function does the whole Z80 simulation. It consists on a
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for(;;) loop (as stated on Marat's Fayzullin HOWTO -How to
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Write a Computer Emulator-) which fetchs the next opcode,
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interprets it (using a switch statement) and then it's
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executed in the right CASE: of that switch. I've put the different
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case statements into C files included here with #include to
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make this more readable (and programming easier! :).
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This function will change regs->ICount register and will execute
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an interrupt when it reaches 0 (or <0). You can then do anything
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related to your machine emulation here, using the Z80Hardware()
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function. This function must be filled by yourself: put there
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the code related to the emulated machine hardware, such as
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screen redrawing, sound playing and so on. This functions can
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return an special value to make Z80Run stop the emulation (and
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return to the caller): that's INT_QUIT. If there is time to
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execute an interrupt, please return INT_IRQ or INT_NMI. Return
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INT_NOINT if there is no time for an interrupt :) .
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Z80Execute() will change PC and all the z80 registers acording
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to the executed opcode, and those values will be returned when
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a INT_QUIT is received.
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Pass as numcycles the number of clock cycle you want to execute
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z80 opcodes for or < 0 (negative) to execute "infinite" opcodes.
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===================================================================*/
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word Z80Run( Z80Regs *regs, int numcycles )
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{
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/* opcode and temp variables */
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register byte opcode;
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eword tmpreg, ops, mread, tmpreg2;
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unsigned long tempdword;
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register int loop;
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unsigned short tempword;
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/* emulate <numcycles> cycles */
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loop = (regs->ICount - numcycles);
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/* this is the emulation main loop */
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while( regs->ICount > loop )
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{
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#ifdef DEBUG
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/* test if we have reached the trap address */
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if( regs->PC.W == regs->TrapAddress && regs->dobreak != 0 )
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return(regs->PC.W);
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#endif
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if( regs->halted == 1 )
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{ r_PC--; AddCycles(4); }
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/* read the opcode from memory (pointed by PC) */
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opcode = Z80ReadMem(regs->PC.W);
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regs->PC.W++;
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/* increment the R register and decode the instruction */
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AddR(1);
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switch(opcode)
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{
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#include "opcodes.c"
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case PREFIX_CB:
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AddR(1);
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#include "op_cb.c"
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break;
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case PREFIX_ED:
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AddR(1);
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#include "op_ed.c"
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break;
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case PREFIX_DD:
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case PREFIX_FD:
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AddR(1);
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if( opcode == PREFIX_DD )
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{
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#define REGISTER regs->IX
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regs->we_are_on_ddfd = WE_ARE_ON_DD;
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#include "op_dd_fd.c"
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#undef REGISTER
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}
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else
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{
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#define REGISTER regs->IY
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regs->we_are_on_ddfd = WE_ARE_ON_FD;
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#include "op_dd_fd.c"
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#undef REGISTER
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}
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regs->we_are_on_ddfd = 0;
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break;
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}
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/* patch ROM loading routine */
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// address contributed by Ignacio Burgueño :)
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// if( r_PC == 0x0569 )
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if( r_PC >= 0x0556 && r_PC <= 0x056c )
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Z80Patch( regs );
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/* check if it's time to do other hardware emulation */
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if( regs->ICount <= 0 )
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{
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tmpreg.W = Z80Hardware(regs);
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regs->ICount += regs->IPeriod;
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loop = regs->ICount + loop;
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/* check if we must exit the emulation or there is an INT */
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if( tmpreg.W == INT_QUIT )
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return( regs->PC.W );
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if( tmpreg.W != INT_NOINT )
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Z80Interrupt( regs, tmpreg.W );
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}
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}
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return(regs->PC.W);
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}
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/*====================================================================
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void Z80Interrupt( Z80Regs *regs, word ivec )
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===================================================================*/
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void Z80Interrupt( Z80Regs *regs, word ivec )
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{
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word intaddress;
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/* unhalt the computer */
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if( regs->halted == 1 )
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regs->halted = 0;
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if( regs->IFF1 )
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{
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PUSH(PC);
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regs->IFF1 = 0;
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switch(regs->IM)
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{
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case 0: r_PC = 0x0038; AddCycles(12); break;
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case 1: r_PC = 0x0038; AddCycles(13); break;
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case 2: intaddress = (((regs->I & 0xFF)<<8) | 0xFF);
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regs->PC.B.l = Z80ReadMem(intaddress);
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regs->PC.B.h = Z80ReadMem(intaddress+1);
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AddCycles(19);
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break;
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}
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}
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}
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/*====================================================================
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word Z80Hardware(register Z80Regs *regs)
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Do here your emulated machine hardware emulation. Read Z80Execute()
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to know about how to quit emulation and generate interrupts.
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===================================================================*/
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word Z80Hardware( register Z80Regs *regs )
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{
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if(
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debug != 1 // && scanl >= 224
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)
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{
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;
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}
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return( INT_IRQ );
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}
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/*====================================================================
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void Z80Patch( register Z80Regs *regs )
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Write here your patches to some z80 opcodes that are quite related
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to the emulated machines (i.e. maybe accessing to the I/O ports
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and so on), such as ED_FE opcode:
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case ED_FE: Z80Patch(regs);
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break;
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This allows "BIOS" patching (cassette loading, keyboard ...).
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===================================================================*/
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void Z80Patch( register Z80Regs *regs )
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{
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///!!! if( tapfile != NULL )
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///!!! {
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///!!! LoadTAP( regs, tapfile );
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///!!! POP(PC);
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///!!! }
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/*
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if( strlen(tapfile) != 0 )
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{
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if( LoadTapFile( regs, tapfile ) )
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{ POP(PC); }
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}
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else
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{
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FileMenu( tfont, 3, tapfile );
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if( strlen(tapfile) != 0 )
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if( LoadTapFile( regs, tapfile ) )
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{ POP(PC); }
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}
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*/
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}
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/*====================================================================
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byte Z80Debug( register Z80Regs *regs )
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This function is written for debugging purposes (it's supposed to
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be a debugger by itself!). It will debug a single opcode, given
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by the current PC address.
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Return DEBUG_OK to state success and DEBUG_QUIT to quit emulation.
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===================================================================*/
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byte Z80Debug( register Z80Regs *regs )
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{
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return( DEBUG_QUIT );
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}
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/*====================================================================
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byte Z80MemRead( register word address )
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This function reads from the given memory address. It is not inlined,
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and it's written for debugging purposes.
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===================================================================*/
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byte Z80MemRead( register word address, Z80Regs *regs )
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{
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return(Z80ReadMem(address));
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}
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/*====================================================================
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void Z80MemWrite( register word address, register byte value )
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This function writes on memory the given value. It is not inlined,
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ands it's written for debugging purposes.
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===================================================================*/
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void Z80MemWrite( register word address, register byte value, Z80Regs *regs )
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{
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Z80WriteMem( address, value, regs );
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}
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/*====================================================================
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byte Z80InPort( register word port )
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This function reads from the given I/O port. It is not inlined,
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and it's written for debugging purposes.
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===================================================================*/
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byte Z80InPort( register word port )
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{
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int porth;
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int code = 0xFF;
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porth = port >> 8;
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if (!(porth & 0x01)) code &= fila[4][1];
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if (!(porth & 0x02)) code &= fila[3][1];
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if (!(porth & 0x04)) code &= fila[2][1];
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if (!(porth & 0x08)) code &= fila[1][1];
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if (!(porth & 0x10)) code &= fila[1][2];
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if (!(porth & 0x20)) code &= fila[2][2];
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if (!(porth & 0x40)) code &= fila[3][2];
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if (!(porth & 0x80)) code &= fila[4][2];
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/*
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issue 2 emulation, thx to Raul Gomez!!!!!
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I should implement this also:
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if( !ear_on && mic_on )
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code &= 0xbf;
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where earon = bit 4 of the last OUT to the 0xFE port
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and micon = bit 3 of the last OUT to the 0xFE port
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*/
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code &= 0xbf;
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if( (port & 0xFF) == 0xFF )
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{
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if( (rand() % 10) > 7 ) return(0xff);
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else return( rand()%0xFF );
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}
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return( code );
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}
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/*====================================================================
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void Z80OutPort( register word port, register byte value )
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This function outs a value to a given I/O port. It is not inlined,
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and it's written for debugging purposes.
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===================================================================*/
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void Z80OutPort( register Z80Regs *regs,
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register word port, register byte value )
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{
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/* change border colour */
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if( ! (port & 0x01) )
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regs->BorderColor = (value & 0x07);
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}
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/*====================================================================
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static void Z80FlagTables ( void );
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Creates a look-up table for future flag setting...
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Taken from fuse's sources. Thanks to Philip Kendall.
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===================================================================*/
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void Z80FlagTables(void)
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{
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int i,j,k;
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byte parity;
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for(i=0;i<0x100;i++) {
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sz53_table[i]= i & ( FLAG_3 | FLAG_5 | FLAG_S );
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j=i; parity=0;
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for(k=0;k<8;k++) { parity ^= j & 1; j >>=1; }
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parity_table[i]= ( parity ? 0 : FLAG_P );
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sz53p_table[i] = sz53_table[i] | parity_table[i];
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}
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sz53_table[0] |= FLAG_Z;
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sz53p_table[0] |= FLAG_Z;
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}
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