Atmel SAM4S Series, Предварительный информационный лист

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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
15.5.4 Error Checking when Programming
Verification on user interface data is performed when accessing the century, year, month, date,
day, hours, minutes, seconds and alarms. A check is performed on illegal BCD entries such as
illegal date of the month with regard to the year and century configured.
If one of the time fields is not correct, the data is not loaded into the register/counter and a flag is
set in the validity register. The user can not reset this flag. It is reset as soon as an acceptable
value is programmed. This avoids any further side effects in the hardware. The same procedure
is done for the alarm.
The following checks are performed:
1. Century (check if it is in range 19 - 20 or 13-14 in Persian mode)
2. Year (BCD entry check)
3. Date (check range 01 - 31)
4. Month (check if it is in BCD range 01 - 12, check validity regarding “date”)
5. Day (check range 1 - 7)
6. Hour (BCD checks: in 24-hour mode, check range 00 - 23 and check that AM/PM flag is
not set if RTC is set in 24-hour mode; in 12-hour mode check range 01 - 12)
7. Minute (check BCD and range 00 - 59)
8. Second (check BCD and range 00 - 59)
Note: If the 12-hour mode is selected by means of the RTC_MR register, a 12-hour value can be pro-
grammed and the returned value on RTC_TIMR will be the corresponding 24-hour value. The
entry control checks the value of the AM/PM indicator (bit 22 of RTC_TIMR register) to determine
the range to be checked.
15.5.5 RTC Internal Free Running Counter Error Checking
To improve the reliability and security of the RTC, a permanent check is performed on the inter-
nal free running counters to report non-BCD or invalid date/time values.
An error is reported by TDERR bit in the status register (RTC_SR) if an incorrect value has been
detected. The flag can be cleared by programming the TDERRCLR in the RTC status clear con-
trol register (RTC_SCCR).
Anyway the TDERR error flag will be set again if the source of the error has not been cleared
before clearing the TDERR flag. The clearing of the source of such error can be done either by
reprogramming a correct value on RTC_CALR and/or RTC_TIMR registers.
The RTC internal free running counters may automatically clear the source of TDERR due to
their roll-over (i.e. every 10 seconds for SECONDS[3:0] bitfield in RTC_TIMR register). In this
case the TDERR is held high until a clear command is asserted by TDERRCLR bit in
RTC_SCCR register.
15.5.6 Updating Time/Calendar
To update any of the time/calendar fields, the user must first stop the RTC by setting the corre-
sponding field in the Control Register. Bit UPDTIM must be set to update time fields (hour,
minute, second) and bit UPDCAL must be set to update calendar fields (century, year, month,
date, day).
Then the user must poll or wait for the interrupt (if enabled) of bit ACKUPD in the Status Regis-
ter. Once the bit reads 1, it is mandatory to clear this flag by writing the corresponding bit in
RTC_SCCR. The user can now write to the appropriate Time and Calendar register.