MRF24J40_08 Datasheet, PDF (121/152 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:
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
© 2008 Microchip Technology Inc.
Preliminary
DS39776B-page 119