Post by thread:weird behaviour of a 16C84 ...

Hi, While testing the code for a send only serial transmition from a PIC 16C84 to a PC I noticed something realy odd behaviour of the programm running on my pic. It4s consist of a loop which just count4s up a byte in the range from D'65' to D'126' ( viewable ASCII ) and send this char to the PC. the byte is simply incremented with a "incf" instruction. while testing once, I noticed that i got e.g. "AEIM ..." insted of the expected "ABCDEFGHI..." - the byte seemed to be not simply incremented, it was added with 4. After resetting the PIC the PIC worked "normal" again. ( means sending "ABCDE... ) while I couldn4t make the PIC showing this odd behaviour again, I4m still wondering how this could happen. will evetually the incf opcode have the opportunity to increment by two ( caused by a erreanous bit in PGM memory ) ? Any Ideas ?

On Mon, 19 Oct 1998, Stefan Sczekalla-Waldschmidt wrote: > while testing once, I noticed that i got e.g. "AEIM ..." insted of > the expected "ABCDEFGHI..." - the byte seemed to be not simply > incremented, it was added with 4. I'm almost certain that by connecting a variable PSU to the PIC and increasing the voltage very slowly from 0 you will be able to duplicate this and other strange things ;). The PIC is not alone on this, it's the state machine that implements the core in the PIC that can assume invalid states if not reset properly. Peter