SH3000UM SEMTECH [Semtech Corporation], SH3000UM Datasheet - Page 19

• Manufacturer Part Number: SH3000UM
• Manufacturer: SEMTECH [Semtech Corporation]

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 may 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 32.768kHz,
producing a minimum interval of 30.5μs and the maxi-
mum 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 signifi cant 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 val-
ue 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 signifi cant byte is read. This pre-
vents errors stemming from the fi nite time between the
readings of individual bytes of the current value.
©2006 Semtech Corp.
POWER MANAGEMENT
POWER MANAGEMENT
Application Information
(continued)
19
Auxillary Functions
Scratchpad RAM
Four bytes of general-purpose RAM reside on the
SH3003.
Voltage Regulator
Pin V
age or a supply source for small loads (< 2mA). A bypass
capacitor may be necessary between this pin and V
the load generates large current transients or a low ripple
reference is required.
REG
can be used as a nominal 2.20V reference volt-
www.semtech.com
SH3003
SS
if