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hi, We are observing the following on ADSP-21060 and ADSP-21160. If an interrupt hits at the third last instrucion before the loop termination, then the 'CURLCNTR' (Current loop counter) gets decremented once on getting out of the ISR and once after executing that instruction. Example code: Inst No 1 lnctr = r0, do REPEAT UNTIL LCE; 2 r0 = r0 + r1; 3 r1 = dm(i4,m7); 4 r4 = r1 + r0; REPEAT: 5 dm(i4,m6) = r4; If the interrupt hits on the instruction number 3, then 'CURLCNTR' decrements after returning from the ISR, and repeats the decrement on execution of instruction number 3. This will mean that the data sanity is lost. Please let me know if this is an anomaly. If this is so is there is any work around for this. thanks and regards, jayanth |
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Interrupt and decrement of CURLCNTR twice?
Started by ●May 23, 2003
Reply by ●June 3, 20032003-06-03
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Hi I think this is due to the loop restriction explained at the page 3-24 of the users manual (21065Lprocessor). I think this is applicable to other SHARC family members also. The restriction says that " The last 3 instructions of a loop cannot be a branch (call, jump or return). This rule has one exception - a non delayed CALL (no DB modifier) paired with an RTS(LR) return from subroutine with loop reentry modifier. You can use the non delayed CALL as one of the last three instruction of a loop (except in a one instruction loop or a two instruction, single iteration loop)." I think RTI instruction is making problem for loop reentry from the interrupt ISR. I did not found a similar situation in interrupts section of the processor manual. I may be wrong, so please correct me also. regards ajith --- In , "kjayanth.rm" <kjay@s...> wrote: > hi, > > We are observing the following on ADSP-21060 and ADSP-21160. > > If an interrupt hits at the third last instrucion before the loop > termination, then the 'CURLCNTR' (Current loop counter) gets > decremented once on getting out of the ISR and once after > executing that instruction. > > Example code: > > Inst No > 1 lnctr = r0, do REPEAT UNTIL LCE; > 2 r0 = r0 + r1; > 3 r1 = dm(i4,m7); > 4 r4 = r1 + r0; > REPEAT: > 5 dm(i4,m6) = r4; > > If the interrupt hits on the instruction number 3, then 'CURLCNTR' > decrements after returning from the ISR, and repeats the decrement on > execution of instruction number 3. This will mean that the data sanity > is lost. > > Please let me know if this is an anomaly. If this is so is there is > any work around for this. > > thanks and regards, > jayanth |
