OSDev.org

Posted: **Tue Aug 27, 2013 7:33 am**

Can someone take a look at this page:

http://wiki.osdev.org/CMOS

go down to the C code example with the heading "Reading All RTC Time and Date Registers". Now look at the do-while loop which contains the comment "This uses the "read registers until you get the same values twice in a row". Is the condition in the do-while loop not wrong? instead of

Code: Select all

    } while( (last_second == second) && (last_minute == minute) && (last_hour == hour) &&
               (last_day == day) && (last_month == month) && (last_year == year) &&
               (last_century == century) );

would you not want its negation:

Code: Select all

    } while( ! (last_second == second) && (last_minute == minute) && (last_hour == hour) &&
               (last_day == day) && (last_month == month) && (last_year == year) &&
               (last_century == century) );

Posted: **Tue Aug 27, 2013 8:59 am**

Hi bwat - you do realize you didn't actually negate the full expression - just one of its terms?

Posted: **Tue Aug 27, 2013 11:37 am**

Well spotted! The idea was to negate the entire conjunction not just the first conjunct.

Posted: **Tue Aug 27, 2013 9:39 pm**

It looks correct to me:
Fetch new values while they're the same... that is exactly what the coder wanted.

Posted: **Wed Aug 28, 2013 10:29 am**

But the comment in the code is "This uses the "read registers until you get the same values twice in a row" - emphasis mine. Surely reading the same values twice means it has stabilised.

Posted: **Thu Aug 29, 2013 5:11 am**

Hi,

bwat wrote:Can someone take a look at this page:

http://wiki.osdev.org/CMOS

go down to the C code example with the heading "Reading All RTC Time and Date Registers". Now look at the do-while loop which contains the comment "This uses the "read registers until you get the same values twice in a row". Is the condition in the do-while loop not wrong?

It was wrong - I've changed it.

Cheers,

Brendan

Posted: **Thu Aug 29, 2013 1:12 pm**

A big thank you to you and everyone who contributes to the wiki. Your efforts are appreciated!

OSDev.org

Error in CMOS Time and Date code?

Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?

Re: Error in CMOS Time and Date code?