CC2510FX Datasheet, PDF (125/244 Pages) List of Unclassifed Manufacturers – True System-on-Chip with Low Power RF Transceiver and 8051 MCU

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.
13.8.1 Sleep Timer Operation
This section describes the operation of the
timer.
Note: In this section of the document, f_Ref is
used to denote the reference frequency for
the synthesizer.
For CC2510Fx f_ref=f_XOSand for
CC2511Fx,
f _ref
=
f _XOSC
2
When referring to the low power RCOSC,
calibrated values are assumed
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 (f_ref / 750). The timer
can only be used in PM0, PM1, and PM2.
The Sleep Timer has a programmable timing
event called Event 0. While in PM0, PM1, or
PM2, reaching Event 0 will make the
CC2510Fx/CC2511Fx enter active mode.
The time between two consecutive Event 0’s
(t_Event0) 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,
t_Event0 is given by:
C2510Fx / CC2511Fx
t _{Event 0}
=
750
f _ref
⋅ EVENT 0 ⋅ 2^{5⋅WOR _ RES}
If the 32.768 kHz crystal oscillator is used to
clock the Sleep Timer, t_Event0 is calculated as
follows:
t _{Event 0}
=
1
32768
⋅
EVENT 0 ⋅ 2^{5⋅WOR _ RES}
The time from the CC2510Fx/CC2511Fx enters
PM2 until the next Event 0 is programmed to
appear (t_SLEEPmin) should be larger than 11.08
ms when f_ref is 26 MHz and 12 ms when f_ref is
24 MHz (Sleep Timer clocked by the low
power RC oscillator).
t _SLEEPmin
=
750 _{⋅ 384}
f _ref
When the Sleep Timer is clocked by the
32.768 kHz crystal oscillator, t_SLEEPmin = 11.72
ms (384/32768).
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.
If EVENT0 is changed to a value smaller than
the current counter value, an Event 0 will
occur immediately.
SWRS055D
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