PIC Micro Controller Interrupt Routine Library

• Introduction to Interrupts via the 16F877 by William Chops Westfield
• Nested Interrupts
• Saving/restoreing registers
• Multiple source interrupts
• Timer tutorial (incl prescalers) by Andrew Warren
• Deterministic timer interrupts by Bob Ammerman
• Compinsating for ISR time loss in a time sensitve main code loop

USART, I2C, EERAM read/write, port setup, ISR, and full initialization sample from Tony Kübek of Flintab AB [tony.kubek at flintab.com]

JAL Interrupts@, Ubicom SX Interrupts@,

See:

• /techref/piclist/roundweather.htm Adrian Round's PIC Weather Station
• /techref/microchip/language/c/io/qenc-dk.htm PIC C I/O Routine - Quadrature Encoder ISR

Comments:

• The interrupt routine templates at www.embedinc.com/pic have all the save/restore code taken care of, you only need to fill in the actual interrupt handling code. The template for PIC 16 is QQQ_INTR.ASPIC and for PIC 18 is QQQ_INTR18.ASPIC. There is also a complete interrupt driven UART driver with software input and output FIFOs, QQQ_UART.ASPIC.

Questions:

• makiyako@hotmail.com asks:

  hello....i wrote a normal interrupt routine for pic18f452.But it doesn't seem to work.Is there any problem with my save and restore context?Can any one help?Thx
  

  in_serv: 
  
  	MOVWF W_SAVE        ; save W
  	SWAPF STATUS, W     ; save STATUS 
  	MOVWF STATUS_SAVE
  
  uart_ready 
  	btfss      PIR1,RCIF	;; 5 
  	goto       	Main		;if not ready, wait...
  		movf RCREG,W		;recover uart data 
  		bsf LATB,3		;light       RB3 led 
  		movwf   rx_data		;save for later 
  		bsf         INTCON,7	;re-enable interrupts
  
  	SWAPF STATUS_SAVE, W
  	MOVWF STATUS		; restore W and STATUS
  	SWAPF W_SAVE, F
  	SWAPF W_SAVE, W     
  
  	retfie      
  

  James Newton replies: First, I would recommend you check Olins templates and the Microchip sample code. Second, what is wrong? What actually happens when you try the code?

• I'm in a super-tight timescale interrupt situation; I'm generating Timer0 interrupts every 20 µSecs. I need to minimize the save and restore code. If I know I'm working in BANK0, can I skip all the PCLATH or even the BANK0 select code?
  
  Thanks Ted Mawson
• matteo at cnpdia.embrapa.br asks:

  How can I save the data memory bank during a interruption if I'm using a 16f873 that does not have the registers mirrowed in the upper memory. Thanks Matteo

  You can't save the entire data memory bank to somewhere else, because there is nowhere else.

  However, you can save away the bits that indicate which data memory bank is the "current" data memory bank. (The BANKSEL command sets those bits). Those bits are in the "status" register.

  Try the standard Saving/restoreing registers code. That code already saves (and later restores) the "status" register. -- David Cary 2005-12-31

• Charlene Ennis asks:

  Hi I am having trouble geting the interrupts working for the PIC16f628. It seems to go to the interrupt once only. i tried checking the toie flag, as it should toggle between 1 and 0, but it does. Any ideas anyone??? Thanks, Charlene

  Are you sure the global interrupt enable bit is "enabled"?

  Does the interrupt routine end with RETFIE (return from interrupt) ? (Ending an interrupt routine with a "normal" RETURN or GOTO doesn't work -- those would cause the "only interrupts once" problem). -- David Cary 2005-12-31

Interested: