/* Author      : Rick van der Zwet
 * S-number    : 0433373
 * Version     : $Id: datapath.c 365 2007-12-03 08:54:04Z rick $
 * Copyright   : FreeBSD Licence
 * Description : Memory unit
 */

#include <stdlib.h>
#include <stdio.h>
#include <sysexits.h>
#include "datapath.h"
#include "imm.h"
#include "constant.h"
#include "memory.h"

word
select_sx(const sx_control_t control)
{
    word out=0;
    switch (control)
    {
    case NO_COMPONENT:
        out = 0;
        break;
    case A:
        out = a;
        break;
    case B:
        out = b;
        break;
    case TEMP:
        out = temp;
        break;
    case TEMP2:
        out = temp2;
        break;
    case PC:
        out = pc;
        break;
    case MAR:
        out = mar;
        break;
    case MDR:
        out = mdr;
        break;
    case CONST:
        out = constant;
        break;
    case IMM:
        out = imm;
        break;
    default:
        fprintf(stderr, "Switch '%i' not implemented\n", control);
        exit(EX_SOFTWARE);
        break;
    };
    return (out);
}

void
update_state(control_t control)
{
    word temp_destbus;
    word temp_mem;

    constant = constant_call(control.constant);
    imm = imm_call(ir, control.ir);

    /* Going to ALU if activated */
    word in1 = 0;
    word in2 = 0;
    if (control.alu_unit == ALU_STALLED) {
        temp_destbus = 0;
    } else {
        in1 = select_sx(control.s1);
        in2 = select_sx(control.s2);
        temp_destbus = alu(in1, in2, control.alu_unit);
    }

    if (control.c == WRITE)
        c = temp_destbus;
    if (control.temp == WRITE)
        temp = temp_destbus;
    if (control.temp2 == WRITE)
        temp2 = temp_destbus;
    if (control.pc == WRITE)
        pc = temp_destbus;
    if (control.mar == WRITE)
        mar = temp_destbus;
    if (control.mdr == WRITE) {
        if (control.mux == DATAPATH)
            mdr = temp_destbus;
        else if (control.mux == MEMORY)
            mdr = temp_mem;
        else {
            fprintf(stderr, "Mux control not defined\n");
            exit(EX_SOFTWARE);
        }
    }

    /* Memory actions */
    if (control.memory != MEM_STALLED) {
        mem_busy = TRUE;
        temp_mem = mem_operation(mar, mdr, control.memory);
        if (control.ir == WRITE)
            ir = temp_mem;
        if (control.mdr == WRITE && control.mux == MEMORY)
                mdr = temp_mem;
    }


    /* Register actions */
    if (control.a == WRITE && ((control.reg & 1) != 0))
        a = reg[control.register_address_a];
    if (control.b == WRITE && ((control.reg & 2) != 0))
        b = reg[control.register_address_b];
    if ((control.reg & 4) != 0)
        reg[control.register_address_c] = c;
}