Post by thread:[PIC]: 16F877 Howto setup TMR0 iNTERRUPT ?

I've tried to setup timer0 to overflow and generate an interrupt. TMR0 should generate int. at 7680 Hz. From my calculations I can get fairly close: 20MHz / 4 / prescaler 1:128 / my routine 256 = 7812 Hz provided TMR0 is preloaded with value 5 (error=1.7% which is ok) The problem is that the IRQ isnt working... I think there must be something wrong w the init. code below since it never seems to trigger the ISR. ; Setup Timer0 Interrupt with prescaler ; Note: dont preload the TMR0 register here. Its pointless since ; this is only run once at startup. Preload should be done in ISR. ; setup TMR0 OPTION_register ('877 datasheet: page 48) ; OPTION_REG (7:0): RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 Bank0 Movlw b'10000110' ; pull-ups are disabled, Interrupt on fall. edge, TMR0 source internal ; TMR0 source edge inc on low->high, prescaler to timer0, TMR0 rate 1:128 movwf OPTION_REG ; and set our options in the option_reg address ; setup TMR0 INTCON register ('877 datasheet: page 49) ; INTCON (7:0): GIE PEIE T0IE INTE RBIE T0IF INTF RBIF Bank0 movlw b'00100010' ; set flags for TRM0 movwf INTCON ; bsf INTCON, GIE ; and Enable Interrupts ! (PS: formatting looks like shit... but I dare not change font since it could possibly trigger the wrath of the ascii puritists. No names ;-) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Patrick J wrote: > Bank0 (snipped) > movwf OPTION_REG ; and set our options in the option_reg address OPTION_REG is in bank 1... Jason Harper -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

>Yepp, that was it - thanxs ! >/Patrick > >----- Original Message ----- >From: "Jason Harper" >OPTION_REG is in bank 1... > Jason Harper A good reason to use Olin's DBANKIF macro ..... Puts banking code in only if it is needed :)))) See http://www.embedinc.com/pic/ -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu