MRF24J40MB-I Datasheet, PDF (123/156 Pages) Microchip Technology – IEEE 802.15.4™ 2.4 GHz RF Transceiver

MRF24J40
Beacon-Enabled Device mode – Figure 3-18 shows
the Sleep time line for Beacon-Enabled Device mode.
In this mode, the sum of the main and remain counters
is the inactive period of the superframe. The
MRF24J40 will time the inactive period as shown in
Equation 3-3.
EQUATION 3-3:
Inactive Period = (MAINCNT * SLPCLK Period) +
(REMCNT * 50 ns)
The MRF24J40 alerts the host processor on the bound-
ary of the active and inactive portion via a Sleep Alert
Interrupt (SLPIF 0x31<7>). The host microcontroller
Acknowledges the interrupt (SLPACK 0x35<7>), at
which time, the MRF24J40 turns off the 20 MHz main
oscillator. As the main counter counts, when
WAKETIME = MAINCNT, the 20 MHz main oscillator is
turned on. The wake counter counts as the 20 MHz main
oscillator stabilizes. The MRF24J40 alerts the host
processor with a wake-up alert interrupt (0x31<6>).
FIGURE 3-18:
BEACON-ENABLED DEVICE SLEEP TIME LINE
Beacon
Time
Beacon
Beacon Interval (BI)
Active Portion
Superframe
Duration (SD)
Sleep Alert Interrupt
SLPIF (0x31<7>)
Sleep Acknowledge
SLPACK
(0x35<7>)
Inactive Portion
Wake-up Alert Interrupt
WAKEIF (0x31<6>)
Remain
Counter
Counts
20 MHz Main Oscillator
Turned OFF
Main Counter Counts
Wake Counter
Counts (~2 ms)
Remain
Counter
Counts
WAKETIME = MAINCNT
20 MHz Main Oscillator
Turned ON
20 MHz Main
Oscillator Stable
Low-Current
Sleep Period
© 2010 Microchip Technology Inc.
Preliminary
DS39776C-page 123