继C51精确延时函数，再次写的PIC18精确延时函数

wangqh1983

/* PIC18 software interface header */
#define Fosc 11059200                    //XTAL = 11.0592MHz
#define Fcy    (Fosc/4)                    //2764800Hz

void
User_Delay_Ms(uchar number)    //delay=((((num1*4)+4)*num2+6)*number+13)/Fcy        
{
    static unsigned char     num1,
                         num2;
    do
    {
        num2 = 10;
        do
        {
            num1 = Fcy/40322;   
            while(--num1);   
        }while(--num2);   
    }while(--number);   
}
欢迎测试！

wangqh1983

C51精确延时函数地址：
http://www.ourdev.cn/bbs/bbs_content.jsp?bbs_sn=4925141&bbs_page_no=1&search_mode=3&search_text=wangqh1983&bbs_id=9999

JQ_Lin

即C51精确延时函数，再次写的PIC18精确延时函数

即——继
进来后才明白。

wangqh1983

(原文件名:2012-2-18 17-41-27.png)

wangqh1983

可以在头文件定义系统时钟！

(原文件名:2012-2-18 18-28-47.png)

millwood0

usually, you don't need that precise of a delay: something in the rough neighbor would typically work.

plus, if you have interrupt,  your delay routines will produce different actual delays.

"num1 = Fcy/40322;     "

I would redefine 40322 so that it can be easily changed when you move the routine to a different chip / architecture.

"            while(--num1);     "

this will create a problem when num1 is calculated to be 0 - from very low Fcy for example. I would use "while (num1--) continue;" instead.

I use a similar approach, except that mine was built up, from delay(cycles); to delay_us(us) which calls delay() and then delay_ms(ms) which calls delay_us(), all of which is based on pre-defined F_CPU.

this allows the code to be fairly easily ported.

chenhuwyl

感谢！！

wangqh1983

感谢你的评说，不过也确实有道理。
this will create a problem when num1 is calculated to be 0 - from very low Fcy for example. I would use "while (num1--) continue;" instead.
但是这个形参如果输入0，将是错误的；不过也让人很难理解。不会有人需要0ms的延时吧。有些时候要求时序比较严格的情况下，我们可以将总中断关闭。

millwood0

"不会有人需要0ms的延时吧。"

it is about the (predictable) behavior of the code: delay_ms(2) is 1 ms, delay_ms(1) is 1ms, delay_ms(0) is 256ms (or32kms, depending on the data type).

that kind of behavior is unexpected for most people.

wangqh1983

it is about the (predictable) behavior of the code: delay_ms(2) is 1 ms

(原文件名:2012-2-26 7-23-49.png)
这个不会啊，但是输入0是错误的。

wangqh1983

I would use "while (num1--) continue;" instead.

如果将代码改成while(number--);汇编代码将会增加，须从新计算Tcy。

ZYBing

感谢分享！

steaven2000

考虑到中断了吗？呵呵