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Annotation of frontvm/hardware/int.c, revision 1.1

1.1     ! root        1: /*
        !             2:   Hatari
        !             3: 
        !             4:   This code handles our interrupt table. So we do not need to test for every possible
        !             5:   interrupt we add any pending interrupts into a table. We then scan the list if used
        !             6:   entries in the table and copy the one with the least cycle count into the global
        !             7:   'PendingInterruptCount' variable. This is then decremented by the execution loop -
        !             8:   rather than decrement each and every entry (as the others cannot occur before this one)
        !             9:   We have two methods of adding interrupts; Absolute and Relative. Absolute will set values
        !            10:   from the time of the previous interrupt(eg, add HBL every 512 cycles), and Relative
        !            11:   will add from the current cycle time.
        !            12:   Note that interrupt may occur 'late'. Ie, if an interrupt is due in 4 cycles time but
        !            13:   the current instruction takes 20 cycles we will be 16 cycles late - this is handled in
        !            14:   the adjust functions.
        !            15: */
        !            16: 
        !            17: #include "main.h"
        !            18: #include "decode.h"
        !            19: #include "int.h"
        !            20: #include "m68000.h"
        !            21: #include "memAlloc.h"
        !            22: #include "misc.h"
        !            23: #include "video.h"
        !            24: 
        !            25: /* List of possible interrupt handlers to be store in 'PendingInterruptTable', used for 'MemorySnapShot' */
        !            26: void *pIntHandlerFunctions[] = {
        !            27:   NULL,
        !            28:   Video_InterruptHandler_VBL_Pending,
        !            29:   NULL,
        !            30:   NULL,
        !            31:   NULL
        !            32: };
        !            33: 
        !            34: INTERRUPTHANDLER InterruptHandlers[MAX_INTERRUPTS];
        !            35: int nCyclesOver=0;
        !            36: int ActiveInterrupt=0;
        !            37: 
        !            38: 
        !            39: /*-----------------------------------------------------------------------*/
        !            40: /*
        !            41:   Reset interrupts, handlers
        !            42: */
        !            43: void Int_Reset(void)
        !            44: {
        !            45:   int i;
        !            46: 
        !            47:   /* Reset counts */
        !            48:   PendingInterruptCount = 0;
        !            49:   nCyclesOver = 0;
        !            50: 
        !            51:   /* Reset interrupt table */
        !            52:   for(i=0; i<MAX_INTERRUPTS; i++) {
        !            53:     InterruptHandlers[i].bUsed = FALSE;
        !            54:     InterruptHandlers[i].pFunction = pIntHandlerFunctions[i];
        !            55:   }
        !            56: }
        !            57: 
        !            58: 
        !            59: /*-----------------------------------------------------------------------*/
        !            60: /*
        !            61:   Convert interrupt handler function pointer to ID, used for saving
        !            62: */
        !            63: int Int_HandlerFunctionToID(void *pHandlerFunction)
        !            64: {
        !            65:   int i;
        !            66: 
        !            67:   /* Is NULL, return ID 0 */
        !            68:   if (pHandlerFunction==NULL)
        !            69:     return(0);
        !            70: 
        !            71:   /* Scan for function match */
        !            72:   for(i=1; i<MAX_INTERRUPTS; i++) {
        !            73:     if (pIntHandlerFunctions[i]==pHandlerFunction)
        !            74:       return(i);
        !            75:   }
        !            76:   
        !            77:   /* Didn't find one! Oops */
        !            78:   return(0);
        !            79: }
        !            80: 
        !            81: 
        !            82: /*-----------------------------------------------------------------------*/
        !            83: /*
        !            84:   Convert ID back into interrupt handler function, used for restoring
        !            85: */
        !            86: void *Int_IDToHandlerFunction(int ID)
        !            87: {
        !            88:   /* Get function pointer */
        !            89:   return( pIntHandlerFunctions[ID] );
        !            90: }
        !            91: 
        !            92: 
        !            93: /*-----------------------------------------------------------------------*/
        !            94: /*
        !            95:   Find next interrupt to occur, and store to global variables for decrement in instruction decode loop
        !            96: */
        !            97: void Int_SetNewInterrupt(void)
        !            98: {
        !            99:   int LowestCycleCount=999999,LowestInterrupt=0;
        !           100:   int i;
        !           101: 
        !           102:   /* Find next interrupt to go off */
        !           103:   for(i=0; i<MAX_INTERRUPTS; i++) {
        !           104:     /* Is interrupt pending? */
        !           105:     if (InterruptHandlers[i].bUsed) {
        !           106:       if (InterruptHandlers[i].Cycles<LowestCycleCount) {
        !           107:         LowestCycleCount = InterruptHandlers[i].Cycles;
        !           108:         LowestInterrupt = i;
        !           109:       }
        !           110:     }
        !           111:   }
        !           112: 
        !           113:   /* Set new counts, active interrupt */
        !           114:   PendingInterruptCount = (short int)InterruptHandlers[LowestInterrupt].Cycles;
        !           115:   PendingInterruptFunction = InterruptHandlers[LowestInterrupt].pFunction;
        !           116:   ActiveInterrupt = LowestInterrupt;
        !           117: 
        !           118: }
        !           119: 
        !           120: 
        !           121: /*-----------------------------------------------------------------------*/
        !           122: /*
        !           123:   Adjust all interrupt timings, MUST call Int_SetNewInterrupt after this
        !           124: */
        !           125: void Int_UpdateInterrupt(void)
        !           126: {
        !           127:   int CycleSubtract;
        !           128:   int i;
        !           129: 
        !           130:   /* Find out how many cycles we went over (<=0) */
        !           131:   nCyclesOver = PendingInterruptCount;
        !           132:   /* Calculate how many cycles have passed, included time we went over */
        !           133:   CycleSubtract = InterruptHandlers[ActiveInterrupt].Cycles-nCyclesOver;
        !           134: 
        !           135:   /* Adjust table */
        !           136:   for(i=0; i<MAX_INTERRUPTS; i++) {
        !           137:     if (InterruptHandlers[i].bUsed)
        !           138:       InterruptHandlers[i].Cycles -= CycleSubtract;
        !           139:   }
        !           140: }
        !           141: 
        !           142: 
        !           143: /*-----------------------------------------------------------------------*/
        !           144: /*
        !           145:   Adjust all interrupt timings as 'ActiveInterrupt' has occured, and remove from active list
        !           146: */
        !           147: void Int_AcknowledgeInterrupt(void)
        !           148: {
        !           149:   /* Update list cycle counts */
        !           150:   Int_UpdateInterrupt();
        !           151: 
        !           152:   /* Disable interrupt entry which has just occured */
        !           153:   InterruptHandlers[ActiveInterrupt].bUsed = FALSE;
        !           154: 
        !           155:   /* Set new */
        !           156:   Int_SetNewInterrupt();
        !           157: }
        !           158: 
        !           159: 
        !           160: /*-----------------------------------------------------------------------*/
        !           161: /*
        !           162:   Add interrupt from time last one occurred
        !           163: */
        !           164: void Int_AddAbsoluteInterrupt(int CycleTime, int Handler)
        !           165: {
        !           166:   InterruptHandlers[Handler].bUsed = TRUE;
        !           167:   InterruptHandlers[Handler].Cycles = CycleTime + nCyclesOver;
        !           168: 
        !           169:   /* Set new */
        !           170:   Int_SetNewInterrupt();
        !           171: }
        !           172: 
        !           173: 
        !           174: /*-----------------------------------------------------------------------*/
        !           175: /*
        !           176:   Add interrupt to occur from now
        !           177: */
        !           178: void Int_AddRelativeInterrupt(int CycleTime, int Handler)
        !           179: {
        !           180:   InterruptHandlers[Handler].bUsed = TRUE;
        !           181:   InterruptHandlers[Handler].Cycles = CycleTime;
        !           182: 
        !           183:   /* Set new */
        !           184:   Int_SetNewInterrupt();
        !           185: }
        !           186: 
        !           187: 
        !           188: /*-----------------------------------------------------------------------*/
        !           189: /*
        !           190:   Remove a pending interrupt from our table
        !           191: */
        !           192: void Int_RemovePendingInterrupt(int Handler)
        !           193: {
        !           194:   /* Stop interrupt */
        !           195:   InterruptHandlers[Handler].bUsed = FALSE;
        !           196: 
        !           197:   /* Update list cycle counts */
        !           198:   Int_UpdateInterrupt();
        !           199:   /* Set new */
        !           200:   Int_SetNewInterrupt();
        !           201: }
        !           202: 
        !           203: 
        !           204: /*-----------------------------------------------------------------------*/
        !           205: /*
        !           206:   Return TRUE if interrupt is active in list
        !           207: */
        !           208: BOOL Int_InterruptActive(int Handler)
        !           209: {
        !           210:   /* Is timer active? */
        !           211:   if (InterruptHandlers[Handler].bUsed)
        !           212:     return(TRUE);
        !           213: 
        !           214:   return(FALSE);
        !           215: }
        !           216: 
        !           217: 
        !           218: /*-----------------------------------------------------------------------*/
        !           219: /*
        !           220:   Return cycles passed for an interrupt handler
        !           221: */
        !           222: int Int_FindCyclesPassed(int Handler)
        !           223: {
        !           224:   int CyclesPassed, CyclesFromLastInterrupt;
        !           225: 
        !           226:   CyclesFromLastInterrupt = (int)InterruptHandlers[ActiveInterrupt].Cycles-PendingInterruptCount;
        !           227:   CyclesPassed = ((int)InterruptHandlers[Handler].Cycles-CyclesFromLastInterrupt);
        !           228: 
        !           229:   return(CyclesPassed);
        !           230: }

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