Post by thread:after I return from an interupt...

sorry, I'm kind of new to this, but say I've got something in a continuous loop like: circle goto circle waiting for an interupt. when the isr is finished and I use the retfie command, will it increment the program counter to execute the instruction after this one? or if it doesn't is there a way that I can increment the program counter myself? thanks Jonathan Newport

JN: I am not sure exactly what you are trying to do ... but an interrupt does not affect your 'circle' code. If you want to exit circle after the interrupt try this #DEFINE iflag var1,0 ;define bit 0 of GP variable as a flag bcf iflag circle btfss iflag goto circle nocircle . . . then in your isr, include the intsruction bsf iflag > circle goto circle > > waiting for an interupt. when the isr is finished and I use the retfie > command, will it increment the program counter to execute the instruction > after this one? or if it doesn't is there a way that I can increment the > program counter myself? thanks > > Jonathan Newport

> From spam_OUTjnewportTakeThisOuTMAIL.ORION.ORG Wed Jun 24 12:12:45 1998 > X-SMAP-Received-From: outside > X-Comment: mitvma.mit.edu: Mail was sent by orions0.orion.org > X-Sender: jnewport@orionc0 > MIME-Version: 1.0 > Date: Wed, 24 Jun 1998 13:14:41 -0500 > From: "Jonathan M. Newport" <.....jnewportKILLspam@spam@MAIL.ORION.ORG> > Subject: after I return from an interupt... > To: PICLISTKILLspamMITVMA.MIT.EDU > > sorry, I'm kind of new to this, but say I've got something in a continuous > loop like: > > circle goto circle > > waiting for an interupt. when the isr is finished and I use the retfie > command, will it increment the program counter to execute the instruction > after this one? No, you return to the same loop. > or if it doesn't is there a way that I can increment the > program counter myself? thanks No, you can't change the content of an item on the stack. But you can just re-enable interrupts at the end of your interrupt handler, and do a goto to the instruction after the circle instruction, as long as you don't need any addresses on the stack. But if circle is in a subroutine that you need to return from, you can't use this hack. By the way, unless you disable the watchdog timer, this loop will eventually cause a watch- dog reset unless you clear the watchdog timer in the interrupt routine and have the interrupt occur often enough. Usaully what people do is have the interrupt routine send a flag for the base level reoutine to continue. For example bcf some_status_byte,0; circle btfss some_status_byte,0; goto circle and in the interrupt routine: ... bsf some_status_byte,0; ... > > Jonathan Newport >

On Wed, 24 Jun 1998 13:14:41 -0500 "Jonathan M. Newport" <.....jnewportKILLspam.....MAIL.ORION.ORG> writes: >continuous loop like: > >circle goto circle > >waiting for an interupt. when the isr is finished and I use the >retfie >command, will it increment the program counter to execute the >instruction >after this one? No. When the interrupt is done, the program will continue in the endless loop. or if it doesn't is there a way that I can increment >the >program counter myself? You can't change the program counter on the stack (Even if you could, it wouldn't be a very good practice since you'd also have to be sure that it was the endless loop that was interrupted). The most flexible way to do it is to have the ISR set a flag, then test the flag in the main program: (flags is a byte in RAM, and isrdone is a constant from 0 to 7 indicating the function of that bit in flags) [In the ISR] .... bsf flags,isrdone ;Tell main program the int. has occurred. ... retfie [In the main program] bcf flags,0 ;Interrupt hasn't occurred. [Enable interrupts, etc.] waitint btfss flags,isrdone ;Skip if flag is set goto waitint ;Otherwise keep waiting ;Here after interrupt. This technique is very flexible. For example, if the ISR is collecting data being sent serially, it might not set the flag until after a whole byte has been received. The main program would then wait until the byte is complete. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]

> Van: Jonathan M. Newport <EraseMEjnewportspam_OUTTakeThisOuTMAIL.ORION.ORG> > Aan: PICLISTspam_OUTMITVMA.MIT.EDU > Onderwerp: after I return from an interupt... > Datum: woensdag 24 juni 1998 20:14 > > sorry, I'm kind of new to this, but say I've got something in a continuous {Quote hidden}> loop like: > > circle goto circle > > waiting for an interupt. when the isr is finished and I use the retfie > command, will it increment the program counter to execute the instruction > after this one? or if it doesn't is there a way that I can increment the > program counter myself? thanks > > Jonathan Newport As you already have seen, the most general solution to your problem is to check a 'not ready' bit that will be cleared in the interrupt-routine. Another way could be, dependend on the Interrupt-source, to go into 'Sleep'-mode. An interrupt will wake the system and you will continue execution of your program. Greetz, Rudy Wieser