I am developing an application using the RCM3700 development kit and I
have some doubts about setting and getting the time from the RTC. The
way I'm updating and reading the rtc is :
int
GetDateTime_RTC (struct tm *tm)
{
return mktm (tm, read_rtc ());
}
int
SetDateTime_RTC (struct tm *tm)
{
write_rtc (mktime (tm));
return 0;
}
However, the documentation about the tm_rd () function
says that it may return 0 or -1 (if clock read failed), but looking
at the code in rtclock.lib, I see that the function does not return
anything although it should (since it returns an int value):
nodebug
int tm_rd(struct tm *t)
{
mktm(t, SEC_TIMER); // get SEC_TIMER which contains current
time in secs
}
Surely it must be a documentation error, since mktm converts a value
in seconds to a date/time filling the tm structure. It does not access
the RTC.
What I want to know is: could the read_rtc or write_rtc functions fail
on any case to get or set the time from the RTC? It is important for
me to know this, since the application should know the date and time
without mistakes.
Regards
Eduardo
Updating and reading the RTC
Started by ●January 15, 2006
Reply by ●January 15, 20062006-01-15
Eduardo,
I have done some work with the read_rtc() function, so am familiar with how
it works, and I can't see any way it could fail. The RTC is really pretty
simple - just a 48 bit ripple counter and a holding register to latch the
data while you read it. The only tricky thing is that it is possible to
latch the data in the middle of a rollover, and so get bogus data.
Read_rtc() handles this by reading the RTC repeatedly until it reads the
same value twice. I trust it.
Write_rtc I haven't looked at, so can't offer any comment.
Will
> -----Original Message-----
> From: rabbit-semi@rabb...
> [mailto:rabbit-semi@rabb...] On Behalf Of esabaj
> Sent: Sunday, January 15, 2006 11:52
> To: rabbit-semi@rabb...
> Subject: [rabbit-semi] Updating and reading the RTC
>
> I am developing an application using the RCM3700 development
> kit and I have some doubts about setting and getting the time
> from the RTC. The way I'm updating and reading the rtc is :
>
> int
> GetDateTime_RTC (struct tm *tm)
> {
> return mktm (tm, read_rtc ());
> }
>
> int
> SetDateTime_RTC (struct tm *tm)
> {
> write_rtc (mktime (tm));
> return 0;
> }
>
> However, the documentation about the tm_rd () function says
> that it may return 0 or -1 (if clock read failed), but
> looking at the code in rtclock.lib, I see that the function
> does not return anything although it should (since it returns
> an int value):
>
> nodebug
> int tm_rd(struct tm *t)
> {
> mktm(t, SEC_TIMER); // get SEC_TIMER which contains current
> time in secs
> }
>
> Surely it must be a documentation error, since mktm converts
> a value in seconds to a date/time filling the tm structure.
> It does not access the RTC.
>
> What I want to know is: could the read_rtc or write_rtc
> functions fail on any case to get or set the time from the
> RTC? It is important for me to know this, since the
> application should know the date and time without mistakes.
>
> Regards
> Eduardo >
> Yahoo! Groups Links >
I have done some work with the read_rtc() function, so am familiar with how
it works, and I can't see any way it could fail. The RTC is really pretty
simple - just a 48 bit ripple counter and a holding register to latch the
data while you read it. The only tricky thing is that it is possible to
latch the data in the middle of a rollover, and so get bogus data.
Read_rtc() handles this by reading the RTC repeatedly until it reads the
same value twice. I trust it.
Write_rtc I haven't looked at, so can't offer any comment.
Will
> -----Original Message-----
> From: rabbit-semi@rabb...
> [mailto:rabbit-semi@rabb...] On Behalf Of esabaj
> Sent: Sunday, January 15, 2006 11:52
> To: rabbit-semi@rabb...
> Subject: [rabbit-semi] Updating and reading the RTC
>
> I am developing an application using the RCM3700 development
> kit and I have some doubts about setting and getting the time
> from the RTC. The way I'm updating and reading the rtc is :
>
> int
> GetDateTime_RTC (struct tm *tm)
> {
> return mktm (tm, read_rtc ());
> }
>
> int
> SetDateTime_RTC (struct tm *tm)
> {
> write_rtc (mktime (tm));
> return 0;
> }
>
> However, the documentation about the tm_rd () function says
> that it may return 0 or -1 (if clock read failed), but
> looking at the code in rtclock.lib, I see that the function
> does not return anything although it should (since it returns
> an int value):
>
> nodebug
> int tm_rd(struct tm *t)
> {
> mktm(t, SEC_TIMER); // get SEC_TIMER which contains current
> time in secs
> }
>
> Surely it must be a documentation error, since mktm converts
> a value in seconds to a date/time filling the tm structure.
> It does not access the RTC.
>
> What I want to know is: could the read_rtc or write_rtc
> functions fail on any case to get or set the time from the
> RTC? It is important for me to know this, since the
> application should know the date and time without mistakes.
>
> Regards
> Eduardo >
> Yahoo! Groups Links >
