SH3002 Datasheet, PDF (10/22 Pages) Semtech Corporation – Reset Management and Clock Management Support IC for Microcontrollers

SH3002 MicroBuddy™
SYSTEM MANAGEMENT
Periodic Interrupt / Wakeup Timer
Simple and versatile, the Periodic Interrupt / Wakeup
Timer can be used to create very accurate recurring
interrupts for use by the host micro. With some minimal
software support from the host processor, it can also be
used to create alarms, with practically unlimited duration.
While the timer is running, the host processor can be
halted, consuming no energy. The interrupt wakes up
the processor, which can perform the requisite task and
go back to sleep, until the next periodic interrupt.
This mode of operation can achieve extremely low
average power consumption.
A 32-bit counter clocked by 32.768 kHz, producing a
minimum interval of 30.5 µs and the maximum interval of
36.4 hours, creates the Timer.
After reset, the Timer is stopped until the new value
for the time interval is written into the 4-byte Time
Interval register. When the least significant byte (LSB) is
written, the whole value is moved to the Time Interval
latch, the counter is reset and starts to increment with
the 32.768 kHz clock.
When the 32-bit comparator detects a match, an
interrupt is generated and the counter is reset and starts
the next timing cycle.
Although the counter cannot be written to, the
current value from the counter can be read at any time.
The whole 32-bit value is loaded into the 32-bit Current
Timer Value latch when the least significant byte is read.
This prevents errors stemming from the finite time
between the readings of individual bytes of the current
value.
Auxiliary functions
Voltage Regulator
Pin VREG can be used as a nominal 2.20 V reference
voltage or a supply source for small loads (<2 mA). A
bypass capacitor might be necessary between this pin
and VSS if the load generates large current transients or
a low ripple reference is required.
32.768 kHz
LSB
LOAD 32-bit Latch
32-bit Counter
RESET
MSB
Current Timer
Value
32-bit Comparator
LOAD 32-bit Latch
LSB ^{32-bit Time Interval} MSB
Interrupt
Logic
Serial I/O
IO/INT
14
Figure 6. Periodic Interrupt / Wakeup timer
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