Freescale MC9S08单片机芯定时器5

中心对齐的脉宽调制模式波形如图8-3所示。

在这种模式下，产生的脉宽调制信号的周期和占空比都是其对应的计数器的2倍。计数器的计数将经历递减和递增两个过程：每个周期的开始，TPMxMOD计数器开始从预置值递减；当递减到输出比较计数器的预置值时，输出电平翻转，计数器继续递减；当计数器递减到0后，开始递增的过程，递增到再次与输出比较计数器预置值相同时，输出电平翻转；计数器继续递增到TPMxMOD计数器预置值后，当前周期结束。由于存在2倍的关系，在中心对齐的脉宽调制模式下，TPMxMOD和输出比较计数器的预置值应限定在0x0001~0x7FFF之间。如果设置为0或者超出0x7FFF，将导致脉宽调制为0占空比或者100%占空比。

定时器中断程序设计：

# include<hidef.h> /* for EnableInterrupts macro */

# include<MC9S08AW60.h> /* include peripheral declarations */

char value;

void main(void){

DisableInterrupts; /* disable Interrupts */

/* Initialize Keybord */

PTADD=0x0F; /* Set

PTAPE=0XF0; /* Internal Pullup Enable bits 7-4 */

PTAD=0x00;

KBI1PE=0xF0; /* Enable

KBI1SC=0x06; /* Keybord Interrupt Enable and event on falling edges*/

/* sensitive*/

/* Initialize TPM */

TPM1SC=0x4F; /* Enable TOF Interrupt and use bus clock */

TPM1MOD=0x4400;

PTBDD=0xFF; /* Set Port B as output */

PTBD=0xFF;

value=0x00;

EnableInterrupts; /* enable interrupts */

for(;;){

__RESET_WATCHDOG(); /* feeds the dog */

} /* loop forever */

}

interrupt Keybord(){

char result;

unsigned int i;

/* Cross scan to acquire Key in code */

result=PTAD;

KBI1PE=0x00;

PTADD=0xF0;

PTAPE=0x0f;

PTAD=0x00;

result |=PTAD;

/* Change TPM time setting judge by key in code */

switch(result){

case 0xee:

TPM1MOD=0x4000;

break;

case 0xee:

TPM1MOD=0x4000;

break;

case 0xed:

TPM1MOD=0x3C00;

break;

case 0xeb:

TPM1MOD=0x3800;

break;

case 0xe7:

TPM1MOD=0x3400;

break;

case 0xde:

TPM1MOD=0x3000;

break;

case 0xdd:

TPM1MOD=0x2C00;

break;

case 0xdb:

TPM1MOD=0x2800;

break;

case 0xd7:

TPM1MOD=0x2400;

break;

case 0xbe:

TPM1MOD=0x2000;

break;

case 0xbd:

TPM1MOD=0x1C00;

break;

case 0xbb:

TPM1MOD=0x1800;

break;

case 0xb7:

TPM1MOD=0x1400;

break;

case 0x7e:

TPM1MOD=0x1000;

break;

case 0x7d:

TPM1MOD=0x0C00;

break;

case 0x7b:

TPM1MOD=0x0800;

break;

case 0x77:

TPM1MOD=0x0400;

break;

}

for(i=0;i<=20000;i++) __RESET_WATCHDOG();

/* Resume to initial state */

KBI1PE=0xF0;

PTADD=0x0F;

PTAPE=0xF0;

PTAD=0x00;

TPM1CNTH=0x00;

value=0x00;

PTBD=0xFF;

KBI1SC_KBACK=1; /* Keybord interrupt acknowledge */

}

interrupt TPM (){

value++;

PTBD=~value;

TPM1SC_TOF=0; /* TPM interrupt acknowledge */

}

把Keybord中断和TPM中断添加到中断向量表（在prm文件中）中；

VECTOR ADDRESS 0xFFD2 Keybord

VECTOR ADDRESS 0xFFEE TPM

注：整理自网络