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POWER MANAGEMENT

SH3003

POWER MANAGEMENT

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

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 signiﬁcant byte is read. This pre-

vents errors stemming from the ﬁnite time between the

readings of individual bytes of the current value.

Periodic Interrupt/Wakeup Timer

Application Information (continued)

Auxillary Functions

Scratchpad RAM

Four bytes of general-purpose RAM reside on the

SH3003.

Voltage Regulator

Pin VREG can be used as a nominal 2.20V reference volt-

age or a supply source for small loads (< 2mA). A bypass

capacitor may be necessary between this pin and VSS if

the load generates large current transients or a low ripple

reference is required.

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