Using as many internal peripherals as possible.

[louislouis]

In my minimalist mania, I tried using interrupts. On pin RA3 hooked up 10k pullup and pushbutton to ground. On pin RA5 LED. First I tried the On Interrupt statement from PBP not work at all. Then I tried DT Instant interrupts, which worked flawlessly but the code size was a little big.
Then I came up with this. Is it ok to use interrupts like this?
I welcome comments so that I can learn from them.

#CONFIG
  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG

DEFINE INTHAND INT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010

TRISA   =    %011000   ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA  =    %0000     ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256

FVRCON  =    %10011000 ; Internal reference to 2048mV

CM1CON0 =    %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 =    %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V

LATA    =    %000001   ; init state of pin RA0 and RA1, LEDs connected to these pins

T1CON = %00110001      ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000     ; Enable GIE, PEIE, IOCIE
PIE1.0 = 1             ; Enable TMR1IE Owerflow interrupt 
IOCAN.3 = 1            ; Enable RA3 negative edge OnChange interrupt 

; ------------  With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
; pause 10000 ; some stuff here
goto main             

; ------------  INT Handler Routine ---------------
asm
INT:
endasm
IF PIR1.0  THEN LATA = LATA ^ %000011 : PIR1.0 = 0  ; Flash the LEDs on RA0 and RA1 alternately
if IOCAF.3 then LATA = LATA ^ %100000 : IOCAF.3 = 0 ; Toggle LED on Pin RA5 if button on RA3 is pressed
@ RETFIE

It compiles only 58 words, and the main section is empty, ready for some other code.

[richard]

Is it ok to use interrupts like this?

no , you may appear to get away with inserting pbp statements in an ASM interrupt but it is a delusion.
pbp statements set many internal variables to enable complex statements to be evaluated , executing foreign statements from an isr will pollute this process. thats why dt-ints exists.


use asm code in asm interrupts like this

#CONFIG  __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG


DEFINE INTHAND myINT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010


TRISA   =    %011000   ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA  =    %0000     ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256


FVRCON  =    %10011000 ; Internal reference to 2048mV


CM1CON0 =    %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 =    %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V


LATA    =    %000001   ; init state of pin RA0 and RA1, LEDs connected to these pins


T1CON = %00110001      ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000     ; Enable GIE, PEIE, IOCIE
PIE1.0 = 1             ; Enable TMR1IE Owerflow interrupt 
IOCAN.3 = 1            ; Enable RA3 negative edge OnChange interrupt 


; ------------  With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
; pause 10000 ; some stuff here
goto main             


; ------------  INT Handler Routine ---------------
asm
myINT
 movlw 0
 banksel PIR1
 btfsc PIR1,0
 movlw 3
 bcf PIR1,0
 banksel IOCAF
 btfsc IOCAF,3
 iorlw 32
 bcf IOCAF,3
 banksel LATA
 xorwf LATA,f
 RETFIE
endasm