Multiple HPWM's 16F877

**emmett brown** · - 7th October 2006, 02:08

But does it mean that the chips with three pwm's need to be the same frequency? I'll try it in the simulator then run it on the chip Thanks much for your time! Emmett

**emmett brown** · - 10th October 2006, 01:37

Hi group, The PBP manual says that the highest frequency at the HPWM's at any oscillator speed is 32767Hz. Is this correct? I'm looking for 48Khz. Also It says that if two are used they have to be the same frequency. The same frequency if I use three? Don't understand the limitations. Thanks again all! Emmett

**mister_e** · - 10th October 2006, 02:35

It could depend of the PIC too.

BTW @48MHZ, the highest frequency possible by using the calc should be 'round 5 MHZ (even if i have some doubt), 32.xxxKHZ is really low.

HPWM is certainelay limited. To avoid this limitation, you have to write to the CCP register.
Here's a short code snip for 2.5MHZ @ 50% duty cycle on a 16F877.

Code:

DEFINE OSC 20
TRISC=0
DUTY VAR WORD

T2CON=%00000100
PR2=1
DUTY=4
CCP1CON=%00001100 ' PWM MODE
CCP1CON.5=DUTY.1
CCP1CON.4=DUTY.0
CCPR1L=DUTY>>2

START:
      PAUSE 1
      GOTO START