Rainbow Electronics RF22 - Manual (Page 11)

RF22
Version: 0.1 Date: 12/23/2008
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3.2.2.2. SLEEP Mode
In SLEEP mode the LPLDO is enabled along with the Wake-Up-Timer, which can be used to accurately wake-up the
radio at specified intervals. See "8.6. Wake-Up Timer" on page 62 for more information on the Wake-Up-Timer. Sleep
mode is entered by setting enwt=1 (40h) in "Register 07h. Operating Mode and Function Control 1". If an interrupt has
occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current consumption. Also,
the ADC should not be selected as an input to the GPIO in this mode as it will cause excess current consumption.
3.2.2.3. SENSOR Mode
In SENSOR Mode either the Low Battery Detector, Temperature Sensor, or both may be enabled in addition to the
LPLDO and Wake-Up-Timer. The Low Battery Detector can be enabled by setting enlbd = 1 and the temperature
sensor can be enabled by setting ents = 1 in "Register 07h. Operating Mode and Function Control 1". See "8.4.
Temperature Sensor" on page 59 and "8.5. Low Battery Detector" on page 61 for more information on these features. If
an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current
consumption.
3.2.2.4. READY Mode
READY Mode is designed to give a fast transition time to TX mode with reasonable current consumption. In this mode
the Crystal oscillator remains enabled reducing the time required to switch to the TX or RX mode by eliminating the
crystal start-up time. Ready mode is entered by setting xton = 1 in "Register 07h. Operating Mode and Function Control
1". To achieve the lowest current consumption state the crystal oscillator buffer should be disabled. This is done by
setting "Register 62h. Crystal Oscillator/Power-on-Reset Control" to a value of 02h. To exit ready mode, enamp2x (bit
2) of this register must be set back to 0.
3.2.2.5. TUNE Mode
In TUNE Mode the PLL remains enabled in addition to the other blocks enabled in the IDLE modes. This will give the
fastest response to TX mode as the PLL will remain locked but it results in the highest current consumption. This mode
of operation is designed for Frequency Hopping Systems (FHS). Tune mode is entered by setting pllon = 1 in "Register
07h. Operating Mode and Function Control 1". It is not necessary to set xton to 1 for this mode; the internal state
machine automatically enables the crystal oscillator.
3.2.3. TX State
The TX state may be entered from any of the IDLE modes when the txon bit is set to 1 in "Register 07h. Operating
Mode and Function Control 1". A built-in sequencer takes care of all the actions required to transition between states
from enabling the crystal oscillator to ramping up the PA to prevent unwanted spectral splatter. The following sequence
of events will occur automatically when going from STANDBY mode to TX mode by setting the txon bit.
1. Enable the Main Digital LDO and the Analog LDOs.
2. Start up crystal oscillator and wait until ready (controlled by timer).
3. Enable PLL.
4. Calibrate VCO (this action is skipped when the vcocal bit is “0”; default value is “1”).
5. Wait until PLL settles to required transmit frequency (controlled by timer).
6. Activate Power Amplifier and wait until power ramping is completed (controlled by timer).
7. Transmit Packet.
The first few steps may be eliminated depending on which IDLE mode the chip is configured to prior to setting the txon
bit. By default, the VCO and PLL are calibrated every time the PLL is enabled. If the ambient temperature is constant
and the same frequency band is being used these functions may be skipped by setting the appropriate bits in "Register
55h. Calibration Control".
3.2.4. RX State
The RX state may be entered from any of the IDLE modes when the rxon bit is set to 1 in "Register 07h. Operating
Mode and Function Control 1". A built-in sequencer takes care of all the actions required to transition from one of the