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Forum Index : Microcontroller and PC projects : CPU exception
| Author | Message | ||||
jman Guru  Joined: 12/06/2011 Location: New ZealandPosts: 711 |
Hi I was playing around with a rotary encoder and got this error with a Micromite MKII running 4.6B 
After the restart the program crashed as it did not start from the beginning Anybody got any ideas or seen this before. After staring the program again it all seems normal and has not crashed again ? Regards Jman |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3165 |
This exception is caused by the CPU trying to access a non existent address. Normally it indicates a serious bug in MMBasic but because it is not repeatable that does not seem to be the cause. Another cause that I have seen is noise on the power or ground lines to the chip, or the capacitor on Vcap is not up to scratch. The telling symptom is that the exception occurs at random, which seems to match your case. Using a lower CPU speed often reduces the problem although the best course is to correct the power issue. Geoff Geoff Graham - http://geoffg.net |
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| jman Guru Joined: 12/06/2011 Location: New ZealandPosts: 711 |
Hi Geoff Thanks for the reply. The chip is a PIC32MX170F256D-50I/PT so I was running it at 48MHz I have reduced this to 40MHz and the error is gone This only occurs when use a rotary encoder (code from the manual) and you spin the encoder quickly and continually swapping directions. The PCB is a well grounded (copper pour) with lots of decoupling. 5V regulator into a 3.3 regulator. I have tried a known good power source with the same result. Rather odd. I have changed the PIC32MX170F256D-50I/PT and this has cured it at 48Mhz Thanks for the help Jman |
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