fetch.c

/*
 * File: fetch.c
 * Description: Handles the fetching of instructions in the XM-23p Emulator. It updates the program counter and manages the instruction and execution start addresses.
 * Author: Abdulla Sadoun
 * 
 * - Date: 26/06/2024 
 * 
 */
#include "xm23p.h"

// unsigned short timecounter; // time counter
// #define CEX_IS_DISABLED ((fcountbuff == CLEAR) && (tcountbuff == CLEAR))

// void process_instruction(){
// /*
// function to process the instruction
// - it fetches the instruction
// - it decodes the instruction
// - it executes the instruction
// - it increments the time counter
// */
//     fetch(); // fetches the instruction
//     printf("IMARValue:%04X @PC=%04X \n", IMARValue, RegistersValue[PC]); // debug printf

//     while(!(IMARValue == 0x0000 || RegistersValue[PC] == BreakpointValue)) { //|| count >= 50

//         fetch();
//         printf("IMARValue:%04X @PC=%04X\t", IMARValue, RegistersValue[PC]); // debug printf
//         RegistersValue[PC] += 2;
//         ChangedRegistersValue(RegistersValue[PC], PC);


//         timecounter++;

//         int instructionnumber = decode();
//         timecounter++;

//         if (CEX_IS_DISABLED) { // is CEX enabled?
// 			execute(instructionnumber); // executes current instruction. (CEX off)
// 		} else {
//             cex_enabled(instructionnumber); // CEX enabled
//         }

//         //execute(instructionnumber); // executes current instruction. 
//         fetch(); // fetches next instruction
//         timecounter++;
//     } 

//     printf("Breakpoint reached or the end of exec.\n");
// }

void fetch(){ // fetch function
/*
function to fetch the instruction
- it fetches the instruction from memory
- it returns the fetched instruction
*/
    IMARValue = IMEM[RegistersValue[PC]/2]; // because IMEM is unsigned short

    return;
}

// void step(){
// /*
// function to step through the instructions
// - it fetches the instruction
// - it decodes the instruction
// - it executes the instruction
// - it increments the time counter
// */
//     fetch();

//     if(IMARValue == 0x0000 || RegistersValue[PC] == BreakpointValue){
//         printf("Breakpoint reached or the end of exec.\n");
//         return;
//     } else {
//         fetch();
        
//         RegistersValue[PC] += 2;
//         ChangedRegistersValue(RegistersValue[PC], PC);

//         int instructionnumber = decode();

//         execute(instructionnumber); // executes current instruction. 
//         return;
//     }
    
// }

// void cex_enabled(int instructionnumber) {
//     if (cex_condition) {
//         execute(instructionnumber); // executes current instruction.
//         tcountbuff--;               // Decrement True counter
//         if (tcountbuff == CLEAR) {
//             cex_condition = FALSE;  // set CEX condition to False
//         }
//     } else {
//         fcountbuff--;               // Decrement False counter
//         if (fcountbuff == CLEAR) {
//             cex_condition = TRUE;   // Set CEX condition to True
//         }
//     }
// }