1Hz clock using Timer3, 32.768kHz crystal and runs badly on 18F26k22
I have been building clocks for a while and have sometried and tested code which works great on an 18F25k22. I need to add some more features to the device which uses this so I am stepping up to the 18f26k22 just for the larger memory.
When i run the code which worked on the 18f25k22 on the 18f26k22, the clock increments randomly by 2 seconds when it should only increment by 1.
I have a 32.768kHz on the secondary oscillator input pins (with suitable caps)
Using timer 3, no prescaler and prelaod of 128 in TMR3H each epoch.
An interrupt is generated every 1 second when timer 3 rolls over and my code simply increments the 'Seconds' register...when that reaches 60 it is reset and minutes is incremented and so on.
The code has been perfectly behaved on the 25k22, but now, compiled for the 26k22 the seconds counter is sometimes incremented by 2 when it should only increment by 1
I have tried adding new variable for seconds called Seconds2 ( in case it was a memory location issue. I have tried stopping the timer3 from running, T3CON.0 = 0, before writing to it. I have tried everything I can think of, but I can't seem to get it to behave with the 26k22.
I have several boards of identical circuits, whichever has the 26k22 chip has the problem and the fault moves with the chips. I have had this with a batch of SDIP 26k22's and a couple of SOIC 26k22's
I've looked at the .inc files (Pbasic and Mchip's own) and can't see any reason for a difference between these devices, so now I am stuck, is it a Pbasic issue or a MPASM issue ? The only difference between these two chips is that the 26k22 gains 32k more memory over the 25k22, otherwise they seem to be identical.
Has anyone got any experience with something as odd as this ? For comparisons I've used CPFSEQ and CPFSGT instead of the longhand XORLW too, but nothing makes an difference. It is almost as if with the 26k22 version the TMR3 overflow isn't interrupt isn't being cleared and the code is run through twice, but I am clearing the interrupt and reloading the TMR3 registers manually.
Chris
Code:btfss PIR2,1 ; timer 3 rollover interrupt ? (1 second epoch) bra INT_OUT bsf _power btfss PORTA,0 bcf _power bcf T3CON,0 ; stop TMR3 prior to writing to it movlw 128 movwf TMR3H movf _timer3l_buffer,w ; compensation value for low voltage btfss STATUS,Z movwf TMR3L bsf T3CON,0 ; re enable TMR3 after writing bsf _control,6 ; set 1 sec flag bcf PIR2,1 ;clear interrupt incf _seconds2,f movlw 60 xorwf _seconds2,w btfss STATUS,Z bra INT_OUT clrf _seconds2 incf _Minutes,f movlw 60 xorwf _Minutes,w btfss STATUS,Z bra INT_OUT clrf _Minutes incf _Hours,f movlw 24 xorwf _Hours ,w btfss STATUS,Z BRA INT_OUT clrf _Hours bsf _control,2 ; set 'NEW DAY' flag
Originally Posted by BH_epuk
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