Rainbow Electronics AT86RF230 - Manual (Page 13)

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AT86RF230
5131A-ZIGB-06/14/06
4.2.5. RX_ON and BUSY_RX
The RX_ON mode enables the analog and digital receiver blocks and the PLL frequency synthesizer. The
transition from TRX_OFF mode to RX_ON mode is started by setting the TRX_STATE to RX_ON via a SPI write
access to register 0x02 (TRX_STATE).
The receive mode is internally divided into RX_ON mode and BUSY_RX mode. There is no difference between the
modes with respect to the analog radio part. During RX_ON mode, only the preamble detection of the digital signal
processing is running. When a preamble is detected, the digital receiver is turned on, switching to the BUSY_RX
mode.
SLP_TR = 1 is only evaluated in RX_ON mode. When receiving a frame in BUSY_RX mode, the SLP_TR pin has
no effect.
4.2.6. RX_ON_NOCLK
If the radio is listening for an incoming frame and the controller is not running an application, the controller can be
powered down to decrease the total system power consumption. This special power-down scenario for controllers
running in synchronous mode is supported by the AT86RF230 using the state RX_ON_NOCLK.
This state can only be entered by setting SLP_TR = 1 while the IC is in the RX_ON mode. The CLKM pin will then
be disabled 35 clock cycles after the rising edge at the SLP_TR pin. This will enable the controller to complete its
power-down sequence. The reception of a frame is signalized to the controller by a RX_START IRQ (see Figure
7-13). The clock CLKM is turned on once again and the transceiver enters the BUSY_RX state.
The end of the transaction is signaled to the controller by an TRX_END interrupt. After the transaction has been
completed, the transceiver will enter the RX_ON state. The transceiver will only re-enter the RX_ON_NOCLK state
when the SLP_TR has been reset to “0”, and afterwards set to “1” again.
If the transceiver is in the RX_ON_NOCLK state, and the SLP_TR pin is reset to “0”, it will enter the RX _ON state,
and it will again start to supply the micro-controller with the clock signal.
4.2.7. BUSY_TX
Transmitting can only be started from PLL_ON mode. There are two ways to start transmitting: using pin
SLP_TR = 1 or SPI command TX_START in register 0x02 (TRX_STATE). Either of these will cause the IC to enter
BUSY_TX mode.
During the transition to BUSY_TX mode, the PLL frequency shifts 1.5 MHz to enable the different LO frequencies
needed between receive and transmit modes. Transmission of the first data chip of the preamble is delayed by
16 µs to allow PLL settling and PA ramping.
When the end of the frame has been transmitted, the IC will automatically turn off the power amplifier and transition
from the BUSY_TX mode to the PLL_ON mode. The PLL settles to the receiver LO frequency (-1.5 MHz frequency
step).
If the frame transmission was initiated by setting the pin SLP_TR to “1”, a new transmission will only be started
when the pin SLP_TR has been reset to “0” and afterwards to set to “1” again.
4.3. Basic Mode Timing
The following paragraphs depict the method of switching from one mode to another.
4.3.1. Wake-up Procedure
The wake-up procedure from SLEEP mode is shown in Figure 4-2.
Deasserting the pin SLP_TR enables the crystal oscillator. After approximately 0.3 - 0.5 ms, the internal clock
signal is available. After 128 µs the clock signal is delivered at the CLKM pin providing the master clock to the