UM10413
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 1 — 16 December 2011
203 of 268
NXP Semiconductors
UM10413
MPT612 User manual
The power selector module is only implemented in revision A and above; see
.
24.2 Features
•
Measures the passage of time to maintain a calendar and clock
•
Ultra low-power design supports battery powered systems
•
Provides seconds, minutes, hours, day of month, month, year, day of week, and day
of year
•
Can be used with dedicated 32 kHz oscillator or programmable prescaler from APB
clock
•
Dedicated power supply pin can be connected to a battery or to the main 3.3 V
24.3 Description
The Real-Time Clock (RTC) is a set of counters for measuring time when system power is
on and optionally when it is off. It uses little power in Power-down mode. On the MPT612,
the RTC can be clocked by a separate 32.768 kHz oscillator or by a programmable
prescale divider based on the APB clock.
The RTC is powered by its own power supply pin, V
DD(RTC)
, which must be connected to a
battery or to the same 1.8 V core supply used by the rest of the device. Note that the PLL
is disabled when waking up from power-down. See
Section 10.8.8 “PLL and Power-down
for the PLL start-up procedure.
24.4 Architecture
Fig 61. RTC block diagram
aaa-000624
CCLK
INTERRUPT GENERATOR
COUNTER INCREMENT
INTERRUPT ENABLE
ALARM MASK
REGISTER
counter
enables
CLK1
REFERENCE CLOCK
DIVIDER (PRESCALER)
CLK32k
strobe
COMPARATORS
CLOCK GENERATOR
ALARM
REGISTERS
TIME
COUNTERS
RTC OSCILLATOR
MUX