pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 362

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

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Host-Controlled Modules and Host Interface
6.2.12 Oscillator Activity
The RTC oscillator is active if:
The RTC oscillator is disabled in the following cases:
If the RTC oscillator becomes inactive, the following features are dysfunctional/disabled:
6.2.13 Interrupt Handling
The RTC has a single Interrupt Request line, which handles the following three interrupt conditions:
The interrupts are generated if the respective enable bits in CRB register are set prior to an interrupt event occurrence.
Reading the CRC register clears all interrupt flags. Therefore, when multiple interrupts are enabled, the interrupt service
routine should first read and store the CRC register and then deal with all pending interrupts by referring to this stored status.
If an interrupt is not serviced before a second occurrence of the same interrupt condition, the second interrupt event is lost.
Figure 121 illustrates the interrupt timing in the RTC.
V
V
During power-down (V
state. In this case, the oscillator may stop oscillating and memory contents may be corrupted or lost.
Software wrote 00X to DV2-0 bits of CRA register and V
the power consumption from the battery connected to the V
not affected as long as the battery is present at a correct voltage level.
Timekeeping
Periodic interrupt
Alarm
Periodic interrupt
Alarm interrupt
Update end interrupt
CC
BAT
power supply is higher than V
power supply is higher than V
BAT
only), if the battery voltage drops below V
Flags (and IRQ) are reset at the conclusion of CRC read
or by reset.
A = Update In Progress bit high before
B = Periodic interrupt to update
C = Update to Alarm Interrupt = 30.5 s
P = Period is programed by RS3-0 of CRA
Bit 7
of CRA
Bit 4
of CRC
Bit 6
of CRC
Bit 5
of CRC
= Period (periodic int) / 2 + 244 s
CCON
update occurs = 244 s
BATMIN
Figure 121. Interrupt/Status Timing
, independent of the battery voltage, V
whether or not V
B
244 s
P/2
30.5 s
362
P
CC
BAT
(Continued)
CC
is removed. This disables the oscillator and decreases
A
is present.
pin. When disabling the oscillator, the CMOS RAM is
C
BATMIN
P/2
, the PC87591x may enter Battery Fail
BAT
.
Revision 1.07