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Real-Time Clock Registers
17-16
élanSC520 Microcontroller Register Set Manual
RTC Control B (RTCCTLB)
I/O Address 70h/71h
RTC Index 0Bh
Register Description
The RTC Control B register is used to temporarily inhibit RTC updates is in progress, to enable RTC interrupts, and
to control date encoding, 12/24-hour mode, and daylight savings.
.
Bit Definitions
7
6
5
4
3
2
1
0
Bit
SET
PER_
INT_ENB
ALM_
INT_ENB
UPD_
INT_ENB
Reserved
DATE_
MODE
HOUR_
MODE_SEL
DS_ENB
Reset
x
0
0
0
0
x
x
x
R/W
R/W
R/W
R/W
R/W
RSV
R/W
R/W
R/W
Bit
Name
Function
7
SET
Set
0 =Time and date update cycles are enabled and occur once per second.
1 =Time and date update cycles are disabled, and any update in progress is aborted.
The SET bit feature is useful for allowing time and date registers to be updated by software
without being disturbed by an automatic update cycle occurring during the change.
Neither internal functions nor RTC-only resets affect the SET bit.
The SET bit should be set to 1 while changing the DATE_MODE, HOUR_MODE_SEL, or
DS_ENB bits; and cleared afterward.
6
PER_
INT_ENB
Periodic Interrupt Enable
0 =No RTC periodic interrupt is generated.
1 =The RTC periodic interrupt is enabled. When the PER_INT_FLG bit in the RTCSTAC
register transitions from 0 to 1 (see page 17-18), the RTC periodic interrupt latches the
INT_FLG bit in the RTCSTAC register to 1 (see page 17-18). If the PER_INT_FLG bit is 1
when the PER_INT_ENB bit is set by software, the INT_FLG bit is asserted immediately.
The PER_INT_ENB bit is not modified by any internal RTC functions, but is cleared by an
RTC-only reset.
The periodic interrupt rate is configured with the RATE_SEL bit field in the RTCCTLA register
(see page 17-15).
The PER_INT_FLG bit in the RTCSTAC register provides latched status for the RTC periodic
event (see page 17-18).
Before any RTC interrupt is enabled, the RTCMAP register (see page 12-21) must be
configured to route the interrupt to the appropriate interrupt request level and priority.
5
ALM_
INT_ENB
Alarm Interrupt Enable
0 =No RTC alarm interrupt is generated.
1 =The RTC alarm interrupt is enabled. When the ALM_INT_FLG bit in the RTCSTAC register
transitions from 0 to 1 (see page 17-18), the RTC alarm interrupt latches the INT_FLG bit
in the RTCSTAC register to 1 (see page 17-18). If the ALM_INT_FLG bit is 1 when the
ALM_INT_ENB bit is set by software, the INT_FLG bit is asserted immediately.
The ALM_INT_ENB bit is not modified by any internal RTC functions, but is cleared by an
RTC-only reset.
The alarm interrupt time is configured with the RTCALMSEC (page 17-5), RTCALMMIN
(page 17-7), and RTCALMHR (page 17-9) registers.
The ALM_INT_FLG bit in the RTCSTAC register provides latched status for the RTC alarm
event (see page 17-18).
Before any RTC interrupt is enabled, the RTCMAP register (see page 12-21) must be
configured to route the interrupt to the appropriate interrupt request level and priority.