Post by thread:Timer 1 rollover on 16c73

On the 16C73 I'm using Timer 1 free running and need to get the current value of the timer precisely. As you may be reading either high or low bytes as the other is rolling over you must check for the rollover and reread if necessary. This is fine except that I now do not know the timer value precisely as requested. I can recify this by taking a constant from the read value (if it took the long route). Hence the problem, at what point in the fetch/decode stage is the timer incremented. Also if it is a rollover is the carry out asyncronous and at what point would the high byte be incremented based on the carry being set. Here is the offending code: movf TMR1H,W movwf var_timH movf TMR1L,W movwf var_timL //check if overflow movf TMR1H,W subwf var_timH,W btfsc STATUS,2 //bit 2 is zero bit goto Continue movf TMR1H,W movwf var_timH movf TMR1L,W movwf var_timL // Fiddle to get timer value correct independant of // above route to get timer // // If (var_timL <= ?VALUE?-1) // var_timH = var_timH -1 // // var_timL = var_timL - ?VALUE? Continue: ... ... ... Here's hoping someone can help. Cheers. Shane Buckham spam_OUTarl37TakeThisOuTcad.canterbury.ac.nz