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Real-Time Clock Registers
17-18
élanSC520 Microcontroller Register Set Manual
RTC Status C (RTCSTAC)
I/O Address 70h/71h
RTC Index 0Ch
Register Description
The RTC Status C provides RTC interrupt status.
Bit Definitions
7
6
5
4
3
2
1
0
Bit
INT_FLG
PER_
INT_FLG
ALM_
INT_FLG
UPD_
INT_FLG
Reserved
Reset
0
x
x
x
0
0
0
0
R/W
R!
RSV
Bit
Name
Function
7
INT_FLG
Interrupt Request Flag
0 = The RTC interrupt request to the programmable interrupt controller (PIC) is driven
inactive.
1 =When this bit transitions from 0 to 1, the RTC interrupt request to the PIC is driven active,
which generates a CPU interrupt if the RTC interrupt source is enabled at the PIC.
The INT_FLG bit is set to 1 when any one (or more) of the PER_INT_FLG, ALM_INT_FLG, or
UPD_INT_FLG bits transition from 0 to 1 while the corresponding enable bit is asserted in the
RTCCTLB register (see page 17-16). The INT_FLG bit is also set to 1 if an RTC interrupt
source enable bit is written to 1 when the associated flag bit is already asserted.
The INT_FLG bit is cleared after read, and is also cleared by an RTC-only reset.
If the internal RTC is disabled (via the RTC_DIS bit in the ADDDECCTL register, see
page 2-3), the internal signal associated with the INT_FLG status bit is not automatically
disconnected from the PIC. If the intent is to use an external RTC to drive the RTC interrupt
request, then all internal RTC interrupt enables (bits PER_INT_ENB, ALM_INT_ENB, and
UPD_INT_ENB) must be cleared in the RTCCTLB register prior to disabling the internal RTC
(see page 17-16).
6
PER_INT_FLG
Periodic Interrupt Flag
0 =An RTC periodic event has not occurred since this bit was cleared. This bit is cleared after
read and is also cleared by an RTC-only reset.
1 =An RTC periodic event has occurred.
This bit is set when an RTC periodic event occurs regardless of the state of its interrupt
enable bit (the PER_INT_ENB bit in the RTCCTLB register, page 17-16).
The periodic interrupt rate is configured with the RATE_SEL bit field in the RTCCTLA register
(see page 17-15).
5
ALM_INT_FLG
Alarm Interrupt Flag
0 =An RTC alarm event has not occurred since this bit was cleared. This bit is cleared after
read and is also cleared by an RTC-only reset.
1 =An RTC alarm event has occurred.
This bit is set when an RTC alarm event occurs regardless of the state of its interrupt enable
bit (the ALM_INT_ENB bit in the RTCCTLB register, page 17-16).
Alarm events can only occur with a time resolution of one second.
An alarm event occurs when the current time contained in the RTCCURSEC, RTCCURMIN,
and RTCCURHR registers is equal to the alarm setting configured in the RTCALMSEC,
RTCALMMIN, and RTCALMHR registers (see page 17-4 through page 17-9).
The alarm time can contain wildcards for hour, minute, or second settings. A wildcard is any
value from C0h to FFh.