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eff I am using an Interrupt on the same processor to generate a delay that is 255 st ep variable. The max delay is 8.196 ms. I use a 8MHz crystal, so the prescale and post scale would need to be changed. If PR2 is set to zero, the compare will be missed and the time will be the max. The following is the intialization routine. // ---- Timer 2 provides a delay from zero cross to turning on the triac // the max delay for timer 2 is when PR2 reg is set for 255. // Timer 2 counts from zero to a compare with PR2 and causes an interrupt // At 8 MHz, count period = 1,000,000/(8/4) = 0.5 us // The prescale is set to 16 and the post scale is set to 4 for a 64:1 // 256 x 64 x 0.5 = 8.196 ms @ 2 Mhz T2CKPS1 = 1; T1CKPS0 = 1; // divide by 16 prescale TOUTPS3 = 0; TOUTPS2 = 0; TOUTPS1 = 1; TOUTPS0 = 1; // divide by 4 post scale TMR2IF = 0; TMR2IE = 0; // Timer is enabled in the interrrupt The following is the interrupt routine static void // interrupt general_int_service(void) { // GIE = 0; if (TMR1IF) // timer 1 overflow has occured { TMR1IF = 0; TMR1 = TMR1 - 62500; if (timer125 >= 7) { timer125 = 0; } else { ++timer125;} flag125 = timer125; toggle_flag = !toggle_flag; SPARE_2 = toggle_flag; } if ( ZERO_X_FLAG ) { // on zero cross, turn off the triac drive and start tim er 2 ZERO_X_FLAG = 0; OPTO_DRIVE = 0; // turn off the Triac dr ive TMR2IE = 0; // clear int en if necessary TMR2IF = 0; // clear flag PR2 = PR2_preload; TMR2 = 0; // clear any count TMR2ON = 1; // turn on the timer TMR2IE = 1; // enable interrupt OPTO_DRIVE = 0; // turn off the Triac dr ive Time_out_flag = 0; } if (TMR2IF ) { // when timer 2 int, turn off the timer and turn on tria c if in run mode TMR2IE = 0; // disable the timer TMR2IF = 0; // clear the int flag TMR2ON = 0; // clears pre and post scalers TMR2 = 0; // clear count Time_out_flag = 1; if ( Motor_run_flag ) { OPTO_DRIVE = 1; } else { OPTO_DRIVE = 0; } } // GIE =1; } // ***** end int service routine *********************** ***** I hope this helps, Write or call if you have questions. Paul Smargiassi Jeff Wicklein wrote: > > I am trying to come up with a delay routine in for milliseconds using a 480kHz > oscillator and the PIC16C73A. Every routine that I try (even inline > assembler) gives me at least 2ms error. I am using the Hi-tech compiler and > really need help on this. > > Thanks. > > jeff

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