Timer interrupt 16F1827

[Bruce]

Make sure you're in the correct register banks, and it should work just fine. Show whatever code you're having issues with, and someone can probably offer help.

PIE1 is not in the same register bank as the rest of the registers you're writing to.

[Macgman2000]

Hello Bruce,

I am not doing anything that didn't work for the 16F877A. The compiler returns errors for this
code segment. These are the items it returns errors for...T1CON.0 , PIE1.0 and PIR1.0

See below.

[ code]
ASM
myint


; Save and restore FSR and any other registers used
bcf T1CON.0 ; stop timer 1
bcf PIR1.0 ; clear over flow flag
movwf 00h ; load timer for 16,535 * 8 prescaler interrupt on 16 bit timer
movf TMR1H,W
movf TMR1L,W
bsf T1CON.0 ; re-enable timer 1
bcf PIE1.0 ; clear overflow flag just in case

retfie ; Return from interrupt

endasm

[ /code]

[Bruce]

I am not doing anything that didn't work for the 16F877A

Unfortunately, that doesn't really mean much since this PIC type is a totally different animal...

Post everything you have, and I'll give it a shot here compiling it. And - like I mentioned above, not all registers are in the same banks on this PIC as they are in the 877A, and just trying to cut & paste something that was working on an 877A for sure isn't going to work.

This new series PIC is BIG time different than the 877A.

[Darrel Taylor]

; Save and restore FSR and any other registers used
bcf T1CON.0 ; stop timer 1
bcf PIR1.0 ; clear over flow flag
...
bsf T1CON.0 ; re-enable timer 1
bcf PIE1.0 ; clear overflow flag just in case
endasm

At the ASM level, bits are separated from the register with a comma instead of a dot like with PBP.

bcf T1CON,0
bcf PIR1,0
bsf T1CON,0
bcf PIE1,0

However ...
Your ISR does not restore context.
The enable bit is cleared, when the comments say "; clear overflow flag just in case".
An unknown value is moved to address 0 (movwf 00h). Address 0 is usually a PBP system variable.
And the values in TMR1L:H are moved into WREG and nothing is done with them (movf TMR1x,W).

So, beyond the reported errors ... it's not going to work.
Try DT_INTS-14 v1.00.

[Bruce]

Interrupts on these are easier than older 16F parts with the auto restore feature, but you need to make sure you're flipping the right bits to set everything up properly....

Try this.

ASM
  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
  __config _CONFIG2, _PLLEN_OFF & _LVP_OFF & _STVREN_OFF
ENDASM
 
  DEFINE OSC 8
  DEFINE INTHAND Tmr1Int
 
  OSCCON= %01110000
 
  GOTO Init  ' jump over interrupt routine
 
  ASM
Tmr1Int
  ; retfie auto-restores w, status, bsr, fsr and pclath
  bcf   T1CON,TMR1ON ; stop timer 1
  bcf   PIR1,TMR1IF  ; clear over flow flag
  movlw 0xBF         ; load timer for 16,535 * 8 prescaler interrupt on 16 bit timer
  movwf TMR1H        ; load high byte
  movlw 0x69         
  movwf TMR1L        ; load low byte
  bsf   T1CON,TMR1ON ; re-enable timer 1
  movlw 0x01
  xorwf PORTB,f      ; toggle RB0
  retfie             ; Return from interrupt
ENDASM
 
Init:
  PORTB = 0
  TRISB = 0
  CM1CON0.7=0
  CM2CON0.7=0
  ANSELA = 0           ' all digital. A/D disabled
  ANSELB = 0
  PIR1 = 0             ' clear TMR1 int flag
  PIE1 = %00000001     ' TMR1 int enabled
  INTCON = %11000000   ' global & peripheral ints enabled
  T1CON = %00110001    ' TMR1 1:8 prescale, timer1 on
 
Main:
  HIGH 1
  PAUSE 1000
  LOW 1
  PAUSE 1000
  GOTO Main
 
  END

Then check out DT_INTS-14 v1.00

[Macgman2000]

Hello Bruce, Darrel,

Thanks for your help! I read in the data sheet that the context saving is done automatically. So unlike
the 16F877A where a context saving routine example is featured, the 16F1827 does not have any
such routine listed in the data sheet. Just a few lines that mention automatic context saving.

So, using PBP do I need to use context saving using the ASM ISR ?

Nick

[Bruce]

So, using PBP do I need to use context saving using the ASM ISR ?

Nope. If you're using the 16F1827 you don't need to save w, status, bsr, fsr or pclath. It does this for you automagically...

[Darrel Taylor]

OOPs, there's no FAST option on RETFIE with those chips.
It always restores them.

My Bad!