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Hi William, I think, there is a slip of your keyboard. It must be: In the DSP56800 family: JSR pushes PC & SR on the stack. RTS pops SR & PC from the stack, restores PC but discards SR from stack (so SR remains unchanged). RTI pops SR & PC from the stack, and restores both registers. Kind regards, Wim de Haan Exendis B.V. P.O.box 56, 6710 BB Ede Keesomstraat 4, 6716 AB Ede The Netherlands. Tel: +31-(0)318 - 676305 mailto: <mailto:> URL: http://www.exendis.com <http://www.exendis.com/> -----Original Message----- From: Yochum, William [mailto:] Sent: dinsdag 13 april 2004 22:30 To: Corey, Rick Cc: Subject: [motoroladsp] RE: #pragma interrupt / modulus (%) affects interrupts? It doesn't work generally, but in the DSP56800 family: JSR saves SP & SR on the stack. RTS pops SP & SR from the stack, restores SP but discards SR. RTI pops SP & SR from the stack, and restores both registers. So that's why the RTI is safe for a JSR call. -----Original Message----- From: Corey, Rick [mailto:] Sent: Tuesday, April 13, 2004 3:34 PM To: 'Yochum, William'; Michael W. Mann; Subject: RE: #pragma interrupt / modulus (%) affects interrupts? Hi RTI usually restores the SR by popping it off the stack. If you encounter an RTI, but you never pushed the SR onto the stack in a matching "go to ISR" mechanism, the RTI should break the stack most fatally. Maybe you could set up a "callback function" (non-ISR, with no RTI). Have the ISR itself do nothing but call the callback function. Since the ISR shell would contain the RTI, main could call it, too, without blowing the stack. Of course the callback function would have to be re-entrant or have ISR protection. (Maybe callback is the wrong term if it is called directly from inside the ISR.) Rick Corey -----Original Message----- From: Yochum, William [mailto:] Sent: Tuesday, April 13, 2004 3:23 PM To: Michael W. Mann; Subject: Re: #pragma interrupt / modulus (%) affects interrupts? Correct me if I'm wrong, but strictly speaking the difference between an "RTI" and an "RTS" is restoration of the SR register. This MIGHT reenable interrupts, but it doesn't necessarily do so, right? If a "#pragma interrupt" routine was called from the main loop it would simply restore the interrupt status that was active at that time. If interrupts were off they should remain off. -----Original Message----- From: Michael W. Mann [mailto:] Sent: Tuesday, April 13, 2004 2:50 PM To: Subject: [motoroladsp] Re: #pragma interrupt / modulus (%) affects interrupts? --- In , "Pete Becher" <pbecher@d...> wrote: > Hi All, > > I was wondering. If you have a C function that you want to use as an > ISR but also call from the main loop does "#pragma interrupt" work > for both? Does it require 2 different functions? What are the > implications. There are times you can get away with calling a routine that is "#pragma interrupt" enabled from outside of an ISR processing thread. Basically when you call such a routine you are needlessly saving and restoring the core's registers. This is just inefficient. But at the return you are also enabling interrupts. That is the difference between an RTI (return from interrupt) instead RTS (return from subroutine). The #pragma enabled routine will return via RTI. If enabling interrupts at that time causes on harm to your application then you can get away with it. But be sure that it doesn't renable interrupts when you desire to keep them masked. If you don't want this risk then you can code up two separate routines in C. You can also code the routine in assembly and check the SR to see if interrupts are enabled or masked. Then you can save or not save context accordingly. > > Thanks, > Pete _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/motoroladsp <http://www.yahoogroups.com/group/motoroladsp> More Groups: http://www.dsprelated.com/groups.php3 <http://www.dsprelated.com/groups.php3 _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/motoroladsp <http://www.yahoogroups.com/group/motoroladsp> More Groups: http://www.dsprelated.com/groups.php3 <http://www.dsprelated.com/groups.php3 _____ > . |
RE: RE: #pragma interrupt / modulus (%) affects int errupts?
Started by ●April 14, 2004
