4*4 matrix keyboard C51 program

de key_table[16]=
 {0xee,0xed,0xeb,0xe7,0xde,0xdd,0xdb,0xd7,0xbe,0xbd,0xbb,0xb7,0x7e,0x7d,0x7b,0x77};
    key_port=0x0f; //Determine the row and column position
    if(key_port==0x0f)return(0);//Return to 0 if no key is pressed
    delay_ms(10); //Call the delay function to remove the front key jitter.
    if(key_port==0x0f)return(0);//Judge again The purpose is to ensure correct detection
    else
    { 
  for(i=0;i<4;i++) //The following is the classic calculation of key value (to determine the location of the closed key)
        { 
   P0=_cror_(0x7f,i);
     if(key_port_0==0)break;
           if(key_port_1==0)break;
           if(key_port_2==0)break;
           if(key_port_3==0)break;
        }  
     key=key_port; //Get the key value
  for(;key_port!=0x0f; key_port=0x0f); //Wait for the key to be released, the purpose is to remove the back edge key jitter
  for(i=0;key_table[i]!=key && i<16;i++); //Look up the table to get the value of key 0-F
  key=i;
     return(key); //Return to the main calling function with key value
   }
}
/*****************************
   Keyboard scan test main function
**************************/
void main(void)
{
 unsigned char key;
 init_com(); //Serial port initialization 
 while(1)
 {
  key=keyscan();
  if(key!=0)
  {
  com_send_dat(key);
  delay_ms(200);
  }
 }
}