[原创] CH554 改变系统时钟

dcexpert 2017-10-15 18:12 楼主

CH554可以改变系统时钟，CLOCK_CFG寄存器的低三位可以控制系统内部时钟分频系数，从而改变系统工作频率。为了安全，改变CLOCK_CFG寄存器前，需要往安全模式控制寄存器中一次写入0x55和0xAA。
下面程序演示了改变系统时钟频率的方法，将P1.0接地一段时间，就会改变时钟，可以通过LED1的变化看出时钟的变化。

#include <rtx51tny.h>
#include <SST89X5XXRD2.H>
#include "stdint.h"
sbit LED1 = P1^6;
sbit LED2 = P1^7;
sbit BTN = P1^0;
sfr SAFE_MOD = 0xA1;
sfr CLOCK_CFG = 0xB9;
#define FREQ_BASE 6000000UL
#define SYSCLK_187K 0
#define SYSCLK_750K 1
#define SYSCLK_3M 2
#define SYSCLK_6M 3
#define SYSCLK_12M 4
#define SYSCLK_16M 5
#define SYSCLK_24M 6
#define FREQ_187K 187500UL
#define FREQ_750K 750000UL
#define FREQ_3M 3000000UL
#define FREQ_6M 6000000UL
#define FREQ_12M 12000000UL
#define FREQ_16M 16000000UL
#define FREQ_24M 24000000UL
code uint32_t SYSCLK_FREQ[] = (FREQ_187K, FREQ_750K, FREQ_3M, FREQ_6M, FREQ_12M, FREQ_16M, FREQ_24M);
uint32_t F_CPU = FREQ_BASE;
/* only suppot internal clock, support frequence
FREQ_187K
FREQ_750K
FREQ_3M
FREQ_6M (default)
FREQ_12M
FREQ_16M
FREQ_24M
*/
void sysclk(uint8_t freq)
{
if(freq > 6)
return;
F_CPU = SYSCLK_FREQ[freq];
SAFE_MOD = 0x55;
SAFE_MOD = 0xAA;
CLOCK_CFG &= 0xF8;
CLOCK_CFG |= freq;
SAFE_MOD = 0;
}
uint8_t freq=3;
uint8_t btncnt = 0;
job0 () _task_ 0
{
while(1)
{
BTN = 1;
if(BTN == 0)
{
btncnt++;
if(btncnt > 10)
{
btncnt = 0;
freq = (freq+1)%5 + 2;
sysclk(freq);
LED2 = !LED2;
}
}
else
btncnt = 0;
// 0.5s
LED1 = !LED1;
os_wait(K_TMO, 5, 0);
}
}