Rainbow Electronics AT86RF231 User Manual
Page 28
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8111A–AVR–05/08
AT86RF231
Figure 6-15. Sleep and Wake-up Initiated by Asynchronous Microcontroller Timer
Note: Timing figure t
TR2
refer to section
RX_ON and RX_AACK_ON states
For synchronous systems, where CLKM is used as a microcontroller clock source and the SPI
master clock (SCLK) is directly derived from CLKM, the AT86RF231 supports an additional
power-down mode for receive operating states (RX_ON and RX_AACK_ON).
If an incoming frame is expected and no other applications are running on the microcontroller, it
can be powered down without missing incoming frames.
This can be achieved by a rising edge on pin SLP_TR that turns off the CLKM. Then the radio
transceiver state changes from RX_ON or RX_AACK_ON (Extended Operating Mode) to
RX_ON_NOCLK or RX_AACK_ON_NOCLK respectively.
In case that a frame is received (e.g. indicated by an IRQ_2 (RX_START) interrupt) the clock
output CLKM is automatically switched on again.
This scenario is shown in
. In RX_ON state, the clock at pin 17 (CLKM) is
switched off after 35 clock cycles when setting the pin SLP_TR = H.
The CLKM clock frequency settings for 250 kHz and 62.5 kHz are not intended to directly clock
the microcontroller. When using these clock rates, CLKM is turned off immediately when enter-
ing RX_ON_NOCLK and RX_AACK_ON_NOCLK respectively.
In states RX_(AACK)_ON_NOCLK and RX_(AACK)_ON, the radio transceiver current con-
sumptions are equivalent. However, the RX_(AACK)_ON_NOCLK current consumption is
reduced by the current required for driving pin 17 (CLKM).
Figure 6-16. Wake-Up Initiated by Radio Transceiver Interrupt
CLKM
SLP_TR
35 CLKM clock cycles
CLKM off
t
TR2
async timer elapses
(microcontroller)
CLKM
SLP_TR
35 CLKM clock cycles
CLKM off
IRQ
typ. 5 µs
radio transceiver
IRQ issued