使用按位运算符将值从无符号整数（长2个字节）存储到无符号char变量？

Question

How do I put the value of 0x04 in register 4 if the instruction was 1rxy? 1RXY-Load register R with the value at memory address XY

#include <stdio.h>

unsigned char r0,r1,r2,r3,r4,r5,r6,r7,r8,r9,ra,rb,rc,rd,re,rf;

void reg_check(unsigned char reg);
void rxy1(unsigned char reg, unsigned char val);

int main(){
    unsigned char memloc1=0x14;
    unisgned char memloc2=0x04;

    unsigned char temp,reg,val_add;
    temp=(x && 0xFF00) >> 8;

    if (temp = 0xB){
        reg=(memloc1 &0x0F);
        val_add=memloc2;
        rxy1(reg,val_add);
    }

    return 0;
}
void reg_check(unsigned char reg){

}
void rxy1(unsigned char reg, unsigned char val){

The actual instruction is 0x1404, this split into two bytes, memloc1 and memloc2. According to the format of 1rxy, which means to put value "at" memory location xy in register r.

so here register 4 or unsigned char r4 would have to hold the value at memory location 0x04 which would hold some other number.

My question is how do I test for the register variable by determining the "r" or 1"r"xy in 1"4"04 and placing the value held at the location xy into the unsigned char variable r4

for example if memory location 0x04 held 0xFB .

I hope this makes sense.

[edit] Example

#include <stdio.h>
int main(){
    unsigned char r0,r2,r3,r4;
    unsigned char mem1=0x14;  //at lmemory address 00
    unsigned char mem2=0x04;  //at lmemory address 01



    unsigned char reg_val_store=mem1 & 0x0F;


    if( ((mem1= & 0xF0) >> 4) == 0x1){
        if (reg_val_store == 0x4){
            //then put value store at memory address "04" into register 4.
            //and just say for example "0xFD" was at memory location "04"
            //since register value is 4 from the instruction read in 0x1"4"04

            //i want to put 0xFD in the r4 unsigned char variable, how do i do this?
            r4=0xFD; // this is of course correct but the instruction read in changes and 
                // so does the register variable. how do i modify my code for this change?
        }
    }

    return 0;
}

Answer 1

If i understand correctly, you want to put B4 in memory[0] and 04 in memory[1]. Am i right?

This will do that.

memory[0] = ((x & 0xFF00) >> 8 ); //Will put B4 in memory[0]
memory[1] = (x & 0xFF); //Will put 04 in memory[1]

I think, next you want to check B and 4 seperately on memory[0] and then proceed to your next step. Right?

(memory[0] & 0xF0) >> 4 // will give you 0xB
(memory[0] & 0x0F) //will give you 0x4

Is this what you are looking for?

Update : For your reading problem, you should be using this .

while (!feof(f))
{
    fscanf(f,"%X",&inst[i]);
    i++;
}

This reads till EOF and you could use i value after this loop to know how many instructions are read and put it in a variable say n_instr. And then for looping thro' instructions you could use this

while(loop<n_instr) //instead of just loop<80
{
        memory[j] = ((inst[loop] & 0xFF00) >> 8 );
        j=j+2;
        memory[k] = (inst[loop] & 0x00FF);
        k=k+2;

        loop++;
}