C2510Fx / CC2511Fx
13.8 Sleep Timer
The Sleep Timer is used to control when the
CC2510Fx/CC2511Fx exits from PM{0-2} and
hence the Sleep Timer can be used to
implement a wake up functionality which
enables CC2510Fx/CC2511Fx to periodically wake
up to active mode and listen for incoming RF
packets.
750
tEvent0
=
⋅ EVENT0⋅ 25⋅WOR_ RES
fref
If the 32.768 kHz crystal oscillator is used to
clock the Sleep Timer, tEvent0 is calculated as
follows:
1
tEvent0
=
⋅ EVENT0⋅25⋅WOR _ RES
32768
13.8.1 Sleep Timer Operation
This section describes the operation of the
timer.
The time from the CC2510Fx/CC2511Fx enters
PM2 until the next Event 0 is programmed to
appear (tSLEEPmin) should be larger than 11.08
ms when fref is 26 MHz and 12 ms when fref is
24 MHz (Sleep Timer clocked by the low
power RC oscillator).
Note: In this section of the document, fRef is
used to denote the reference frequency for
the synthesizer.
For CC2510Fx
and for
f =fXOS
ref
750
t
=
⋅384
fXOSC
SLEEPmin
CC2511Fx,
fref
fref
=
2
When referring to the low power RCOSC,
calibrated values are assumed
When the Sleep Timer is clocked by the
32.768 kHz crystal oscillator, tSLEEP = 11.72
min
ms (384/32768).
The Sleep Timer consists of a 31-bit counter.
The appropriate bits of this counter are
selected according to a resolution setting
determined by the WORCTRL.WOR_RES
register bits. The Sleep Timer is either clocked
by the 32.768 kHz crystal oscillator or by the
low power RC oscillator (fref / 750). The timer
can only be used in PM0, PM1, and PM2.
13.8.2 Sleep Timer and Power Mode 2
Entering PM2 has to be aligned to a positive
edge on the 32 kHz clock source. Note that
any updates to the compare value, EVENT0,
has to happen prior to this positive edge.
There has to be at least two positive edges on
the 32 kHz clock source between
WORCTRL.WOR_RESET being asserted and
entering PM2.
The Sleep Timer has a programmable timing
event called Event 0. While in PM0, PM1, or
PM2, reaching Event
0
will make the
If EVENT0 is changed to a value smaller than
the current counter value, an Event 0 will
occur immediately.
CC2510Fx/CC2511Fx enter active mode.
The time between two consecutive Event 0’s
(tEvent0) is programmed with a mantissa value
given
by
WOREVT1.EVENT0
and
WOREVT0.EVENT0, and an exponent value set
by WORCTRL.WOR_RES. When using the low
power RC oscillator to clock the Sleep Timer,
tEvent0 is given by:
SWRS055D
Page 125 of 243
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