用MCU的想法寫程式

程式寫久了
總是習慣性的使用* or / or %
卻忘了正在使用的MCU特性是如何

你真的是個軔體工程師嗎？
還是只是個用高階語言寫MCU的工程師

UTC = 0x12345; 

/*    for(i=5;i>=0;i--)      //1           
    {
        dec_temp[i] = UTC % 10;
        UTC /= 10;
    }  */

/*    va = 100000;        //2               
    for(i=0;i<5;i++)
    {                            
        while (UTC>=va)
        {
            UTC -= va;                   
            dec_temp[i]++;             
        }
        va /= 10;                          
    }
    dec_temp[5]=UTC; */        

    /*va = 100000;               //3                           
    while (UTC>=va)
    {
        UTC -= va;                    
        dec_temp[0]++;               
    }    
    va = 10000;                                        
    while (UTC>=va)
    {
        UTC -= va;                    
        dec_temp[1]++;               
    }    
    va = 1000;                                        
    while (UTC>=va)
    {
        UTC -= va;                    
        dec_temp[2]++;               
    }    
    va = 100;                                        
    while (UTC>=va)
    {
        UTC -= va;                    
        dec_temp[3]++;               
    }    
    va = 10;                                        
    while (UTC>=va)
    {
        UTC -= va;                    
        dec_temp[4]++;               
    } 
    
    dec_temp[5]=UTC; */  

/*    va = 100000;                       //4 
    for(i=0;i<5;i++)
    {
        dec_temp[i]=UTC/va;
        UTC -= (dec_temp[i]*va);
        va /=10;
    }*/


  /*dec_temp[0]=UTC/100000;     //5        
    UTC = UTC-(dec_temp[0]*100000);
    dec_temp[1]=UTC/10000;        
    UTC = UTC-(dec_temp[1]*10000);
    dec_temp[2]=UTC/1000; 
    UTC = UTC-(dec_temp[2]*1000);
    dec_temp[3]=UTC/100; 
    UTC = UTC-(dec_temp[3]*100);
    dec_temp[4]=UTC/10;       
    dec_temp[5]=UTC-(dec_temp[4]*10);     */

    /*dec_temp[0]=UTC/100000;      //6           
    UTC = UTC%100000;
    dec_temp[1]=UTC/10000;
    UTC = UTC%10000;    
    dec_temp[2]=UTC/1000;
    UTC = UTC%1000;    
    dec_temp[3]=UTC/100;
    UTC = UTC%100;   
    dec_temp[4]=UTC/10;
    dec_temp[5] =UTC%10;*/

有編號的6個程式碼
所做的事情都一樣
只是把hex to bcd
但如果今天使用的是8bit MCU
雖然結果都是相同的
但程式所執行的時間
和程式的大小可是有很大的差別的

8051:
original code:1205
1.CPU_time:0.00181350 code:1544
2.CPU_time:0.00111800  code:1605
3.CPU_time:0.00034800  code:1534      
4.CPU_time:0.00167875 code:1680
5.CPU_time:0.00080250  code:1830
6.CPU_time:0.00146450  code:1703

6502:
original code:655
1.CPU_time:0.0199435 cpu_cycle:39887    code:1049
2.CPU_time:0.008923   cpu_cycle:17846    code:1125
3.CPU_time:0.000409   cpu_cycle:818        code:1317
4.CPU_time:0.0177185 cpu_cycle:35437    code:1249
5.CPU_time:0.0088335 cpu_cycle:17667    code:1702
6.CPU_time:0.016546   cpu_cycle:33092    code:1489