P89LPC932 PWM DA Conversion

/**************************Asm version**********************************/ 
/*Purpose of the experiment: 
Test the PWM output function of the CCU module (control the duty cycle). 
The duty cycle is controlled by TOR2H, TOR2L, OCRAH, and ORCAL. 
The required voltage value is obtained by controlling the duty cycle 
*/ 

    $NOMOD51

    $INCLUDE(REG932.INC) // 

    PLEEN BIT TCR20.7 

    ORG 0000H 
    AJMP MAIN 
     
    ORG 0100H 
MAIN: 
     MOV P2M1,#0x00 ; Set port mode 
     MOV P2M2,#0xFF ; Set P26,OCA to push-pull output 

     MOV TCR21,#0x04 ; Frequency division operation 

     MOV TOR2H,#0x00 ; Reload value 0x00FF=255 
     MOV TOR2L,#0xF0 ; -> PWM period 
     MOV A,TCR21 
    ANL A,#0x80 
     MOV TCR21,A 

     MOV OCRAH,#0x00 ; Control duty cycle 
     MOV OCRAL,#0xA0 ; 
     MOV A,TCR21 
    ANL A,#0x80 
     MOV TCR21,A 

     MOV CCCRA,#0x01 

    SETB PLEEN ; Start PLL 
    SETB OCA 
LOOP: 
    JNB PLEEN,LOOP ; Wait until PLL locks 

     MOV TCR20,#0x82 ; Set output mode, non-inverting PWM 

    SJMP $ 
    RET 

    END 

/************************************************************/

/**************************C version************************************/ 
/*Purpose of the experiment: 
Test the PWM output function of the CCU module (control the duty cycle). 
The duty cycle is controlled by TOR2H, TOR2L, OCRAH, and ORCAL. 
The required voltage value is obtained by controlling the duty cycle 
*/ 

#include  
sbit PLEEN=TCR20^7; 

main() 
{ 
    P2M1=0x00; //Set port mode 
    P2M2=0xFF; //Set P26, OCA to push-pull output 

    TCR21=0x04; //Frequency division operation 

    TOR2H=0x00; //Reload value 0x00FF=255 
    TOR2L=0xF0; // -> PWM period 
    TCR21|=0x80; 

    OCRAH=0x00; //Control duty cycle 
    OCRAL=0xA0; // 
    TCR21|=0x80; 

    CCCRA=0x01; 

    PLEEN=1; // Start PLL 
    OCA=1; 
    while(PLEEN==0); // Wait until PLL locks 

    TCR20=0x82; // Set output mode, non-inverting PWM 

    while(1);     
} 
/******************************************************************/