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Expalanation Needed about this code

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Hello!

I have a code for BCD to Decimal conversion of date and time

Code: 
        *sec  =  ((*sec & 0x70) >> 4)*10 + (*sec & 0x0F);
        *min  =  ((*min & 0xF0) >> 4)*10 + (*min & 0x0F);
        *hr   =  ((*hr & 0x30) >> 4)*10 + (*hr & 0x0F);
        *week_day =(*week_day & 0x07);
        *day  =  ((*day & 0xF0) >> 4)*10 + (*day & 0x0F);
        *mn   =  ((*mn & 0x10) >> 4)*10 + (*mn & 0x0F);
        *year =  ((*year & 0xF0)>>4)*10+(*year & 0x0F);

sec and minutes both vary from decimal 0 to 59 and bcd 0x00 to 0x59. Then why is the formula for sec and time bcd to decimal transformation is different?

For seconds it is *sec = ((*sec & 0x70 ) >> 4)*10 + (*sec & 0x0F);

For minutes it is *min = ((*min & 0xF0 ) >> 4)*10 + (*min & 0x0F);
 

1. Don't start multiple therads on the same topic.
2. The necessity of masking out some RTC register bits (e.g. seconds.bit7) becomes obvious if you read the datasheet.
 

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