PIC Dead Band Delay Issues

Discussion in 'Programmer's Corner' started by davis1d0, Mar 24, 2009.

  1. davis1d0

    Thread Starter New Member

    Mar 24, 2009
    4
    0
    Hi all,

    I'm using a PIC18F4520 to control 2 transistors. I've setup 2 channel PWM and it is working fine, but when I go to setup the delay between the two channels nothing happens.

    Information on setup:
    osc is 12Mhz
    freq of pwm about 43khz
    duty cycle is about 40% per channel.

    Any help would be great, Thanks
    Code:

    ;Start of main program
    Main:

    banksel TRISC

    movlw b'00000010'
    movwf TRISC
    movlw b'00010000'
    movwf TRISD

    banksel PR2
    movlw b'01000000'
    movwf PR2

    banksel CCPR1L
    movlw b'00011010'
    movwf CCPR1L
    movlw b'10001100'
    movwf CCP1CON

    banksel PWM1CON
    movlw b'00001000' ;Bit 7 sets auto reset
    movwf PWM1CON ;Bits 6:0 Dead Band Delay

    banksel PIR1
    bcf PIR1,TMR2IF

    banksel T2CON
    movlw b'00000100' ; Sets up the timer w/ a 1/16 scaler
    movwf T2CON ; Timer2 Register

    banksel TRISC
    clrf TRISC
    clrf TRISD

    banksel ECCP1AS
    bcf ECCP1AS,ECCPASE
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The hardware is a mystery. If the PWM circuit is controlled by 2 separate pins out of the PIC, turning one off before turning the other on should work. Be nice to see the circuit for confirmation, though.
     
  3. davis1d0

    Thread Starter New Member

    Mar 24, 2009
    4
    0
    thanks for responding....

    there is no hardware off the pwm..... I'm working on getting the built in delay working. I'm using the pwm as the control for my half-bridge converter. At this point the register that is suppose to turn on and determine this delay seems to be doing nothing, I've read through the data sheets many times and I just can't seem to see where I've made an error or if I missed something.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Did you turn off the watchdog timer?
     
  5. davis1d0

    Thread Starter New Member

    Mar 24, 2009
    4
    0
    thanks

    I have it working now.
     
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