RTC System
UG0331 User Guide Revision 15.0
610
18.4.3
Control Register
0x08
R/W
0
The value of the prescaler can be written here. This register
should only be written when the RTC is stopped
—
when the
control register bit 0 reads as a '0'.
0x0C-0x18 R/W
0
Sets and reads the alarm time.
0x20 -0x6C R/W
0
Allows the individual bytes of the date and timer to be read;
and registers can be written when the RTC is running.
Table 607 •
Control
Bit Number
Name
R/W
Reset Value Description
10
Updated
R/W
0
This bit goes High every time the RTC updates the RTC
value. It is cleared by writing '1' to the bit. It allows the CPU
to know that the RTC value is stable and will not change for
the next second.
9
Wakeup_set
W
0
Writing a '1' to this bit asserts the RTC_WAKEUP output and
sets the Wakeup status bit.
8
Wakeup
R
0
This bit is set every time a match occurs. It is cleared by
writing a '1'. Once cleared, it will not be set again until the
next wakeup occurs.
When WAKE_CONTINUE = 0, writing a '1' to this bit restarts
the RTC counting after a wake-up occurs.
Wakeup_clear
W
7
Match
R
0
The RTC value matches the wakeup value. It indicates the
value of the RTC_MATCH output. This is normally active for
1 second while the current time matches the alarm setting.
6
Download
W
0
Writing a '1' causes the current RTC value to be downloaded
to the date/time upload registers initializing the upload value
to the current time. This does not require any
synchronization and takes place immediately.
5
Upload
R/W
0
When '1' is written, the date/time value loaded into the
date/time registers is uploaded to the RTC and stays
asserted until the internal synchronizers complete the
upload.
4
Reset
W
0
When '1' is written, the date/time value is reset and uploaded
to the RTC. This causes the upload bit to be set while the
time is reset.
3
Alarm_off
W
0
When '1' is written, the Alarm is disabled.
When it is read, it indicates that the Alarm is enabled.
It reads back '1' until the internal synchronization completes
and the Alarm is fully disabled.
Alarm_enabled
R
0
2
Alarm_on
W
0
When '1' is written, the Alarm is enabled.
When it is read, it indicates that the Alarm is enabled.
It reads back '1' as soon as the bit is written.
Alarm_enabled
R
0
1
Stop
W
0
When '1' is written, the RTC counter stops.
When it is read, it indicates that the RTC is running.
It reads back as '1' until the internal synchronization
completes and the RTC is fully stopped.
Running
R
0
Table 606 •
Register Map for RTC
(continued)