TQ2440之PMW

设置PB0输出PMW波，驱动蜂鸣器发声：

void Buzzer_Freq_Set( U32 freq )
{
    rGPBCON &= ~3;            //set GPB0 as tout0, pwm output
    rGPBCON |= 2;
        
    rTCFG0 &= ~0xff;        //prescaler = 15+1  timer input clock frequency=PCLK/{prescaler value+1}/{divider value}
    rTCFG0 |= 15;            

    rTCFG1 &= ~0xf;            //mux = 1/8
    rTCFG1 |= 2;            

    rTCNTB0 = (PCLK>>7)/freq;  

    rTCMPB0 = rTCNTB0>>1;    // 50%

    rTCON &= ~0x1f;
    rTCON |= 0xb;            //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0
    rTCON &= ~2;            //clear manual update bit
}

停止蜂鸣器发声：

void Buzzer_Stop( void )
{
    rGPBCON &= ~3;            //set GPB0 as output
    rGPBCON |= 1;
    rGPBDAT &= ~1;
}