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Newbie PWM problem with PIC 16F627

I'm having problems with the PWM module on a PIC 16F627, and I wondered if anyone could help please.

The PIC is clocked at 4MHz, and I've got 6 LEDs on port B, including RB3/CCP1.

I can write simple light-chaser programs, but I'm trying to dim the LED on CCP1, but it is either on, or its off. My program looks like this:

RESET MOVLW B'00000111' ;Disable Comparator modules MOVWF CMCON

BSF STATUS,RP0 ;Switch to bank 1

;Disable pull-ups ;INT on rising edge ;TMR0 to CLKOUT ;TMR0 Incr low2high trans. ;Prescaler assign to Timer0 ;Prescaler rate is 1:256 MOVLW B'11010111' ;Set PIC options MOVWF OPTION_REG ;Write the OPTION register.

CLRF INTCON ;Disable interrupts MOVLW B'11000000' ;RB7 & RB6 are inputs. MOVWF TRISB ;RB5...RB0 are outputs.

MOVLW 0xFF ; all RA are inputs MOVWF TRISA

MOVLW 100 ; set period for PWM MOVWF PR2

BCF STATUS,RP0 ; Switch Back to Bank 0

MOVLW 5 ; set duty cycle (very low) MOVWF CCPR1L

CLRF T2CON ; Reset prescale and postscale to 1:1

MOVLW B'00001100' ; Set PWM mode MOVWF CCP1CON

BSF T2CON,TMR2ON ; enable TMR2

LOOP GOTO LOOP

Just lights the LED on RB3

Any thoughts anyone please?

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Deep Reset
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Deep Reset
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Since the PWM module relys on timer 2, you should also turn that timer on (TMR2ON in T2CON).

HTH Wolfgang

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Use: wolfgang (dot) mahringer (at) sbg (dot) at
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Wolfgang Mahringer

wondered if

Thanks for the reply, but that is what (I think) the "BSF T2CON,TMR2ON" just before the final loop is supposed to do. I'm pretty sure I checked all the bit assignments. I think I need to borrow a scope, though I'm pretty sure the LED is not PWM'ing - I lit the adjacent LED, and the brightness looks the same.

Does anyone know if the PIC simulators allow inspection of the timer registers? I'm not using one at the moment, just taking a suck-it-and-see approach by blowing the code to the controller after each code change.

TIA Deep.

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Deep Reset

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