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84 lines
2.7 KiB
C
84 lines
2.7 KiB
C
19 years ago
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/******************** (C) COPYRIGHT 2003 STMicroelectronics ********************
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* File Name : WDG.c
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* Author : MCD Application Team
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* Date First Issued : 10/24/2003
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* Description : This file provides all the WDG software functions
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********************************************************************************
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* History:
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* 30/11/2004 : V2.0
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* 14/07/2004 : V1.3
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* 01/01/2004 : V1.2
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*******************************************************************************
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THE PRESENT SOFTWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS WITH
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CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE TIME.
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AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY DIRECT, INDIRECT
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OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM THE CONTENT
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OF SUCH SOFTWARE AND/OR THE USE MADE BY CUSTOMERS OF THE CODING INFORMATION
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CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.
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*******************************************************************************/
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#include "wdg.h"
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#ifndef abs
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#define abs(x) ((x)>0 ? (x) : -(x))
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#endif
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/*******************************************************************************
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* Function Name : FindFactors
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* Description : Search for the best (a,b) values that fit n = a*b
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* with the following constraints: 1<=a<=256, 1<=b<=65536
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* Input 1 : n: the number to decompose
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* Input/Output 2 : a: a pointer to the first factor
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* Input/Output 3 : b: a pointer to the second factor
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* Return : None
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*******************************************************************************/
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static void FindFactors(unsigned long n, unsigned int *a, unsigned long *b)
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{
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unsigned long b0;
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unsigned int a0;
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long err, err_min=n;
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*a = a0 = ((n-1)/65536ul) + 1;
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*b = b0 = n / *a;
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for (; *a <= 256; (*a)++)
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{
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*b = n / *a;
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err = (long)*a * (long)*b - (long)n;
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if (abs(err) > (*a / 2))
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{
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(*b)++;
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err = (long)*a * (long)*b - (long)n;
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}
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if (abs(err) < abs(err_min))
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{
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err_min = err;
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a0 = *a;
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b0 = *b;
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if (err == 0) break;
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}
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}
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*a = a0;
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*b = b0;
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}
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/*******************************************************************************
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* Function Name : WDG_PeriodValueConfig
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* Description : Set the prescaler and counter reload value
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* Input : Amount of time (us) needed
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* Return : None
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*******************************************************************************/
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void WDG_PeriodValueConfig ( u32 Time )
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{
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unsigned int a;
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unsigned long n, b;
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n = Time * (RCCU_FrequencyValue(RCCU_PCLK) / 1000000);
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FindFactors(n, &a, &b);
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WDG->PR = a - 1;
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WDG->VR = b - 1;
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}
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/******************* (C) COPYRIGHT 2003 STMicroelectronics *****END OF FILE****/
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