process hung problem + self reset

[eng.alamin]

my serial data source is repeat it self continuously
when the first package arrive the the buffer will be load
and then first (FOR) loop will execute meen while there is serail data looses

after first (FOR LOOP)

the second serial in command will wait for other Sync WORD "SD"
because serial source repeat all data packages continuously (if because of loop
i miss the first appearing of "SD" at the end i'll catch it no matter what )

it works gooood

all data transmit ok and tone appear OK for 9 to 10 min of operation and the two FOR LOOP update continuously

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the hung is apear on tone sound

normaly DTMFOUT sounds apear like this

[toot -- teet -- tut -- tat -- tet - toot --tiit - toot ----> for 10 minuets ]

and then it become sounds like this after 10 min

[teeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeet] -------> till reset