Rainbow Electronics RA01 - Manual (Page 3)

RA01
Version: 1.0 Date: 10/8/2008
Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: [email protected] http://www.hoperf.com 3
Low Battery Voltage Detector
The low battery detector circuit monitors periodically (typ.
8 ms) the supply voltage and generates an interrupt if it
falls below a programmable threshold level.
Wake-Up Timer
The wake-up timer has very low current consumption (4
μA max) and can be programmed from 1 ms to several
hours.
It calibrates itself to the crystal oscillator at every startup
and then at every 30 seconds with an accuracy of ±0.5%.
When the crystal oscillator is switched off, the calibration
circuit switches it back on only long enough for a quick
calibration (a few milliseconds) to facilitate accurate
wake-up timing. The periodic auto-calibration feature can
be turned off.
Event Handling
In order to minimize current consumption, the receiver
supports the sleep mode. Active mode can be initiated by
setting the ex or en bits (in the Configuration Setting or
Receiver Setting Command).
RA01 generates an interrupt signal on several events
(wake-up timer timeout, low supply voltage detection,
on-chip FIFO filled up). This signal can be used to wake
up the microcontroller, effectively reducing the period the
microcontroller has to be active. The cause of the interrupt
can be read out from the receiver by the microcontroller
through the SDO pin.
Interface and Controller
An SPI compatible serial interface lets the user select the
frequency band, center frequency of the synthesizer, and
the bandwidth of the baseband signal path. Division ratio
for the microcontroller clock, wake-up timer period, and
low supply voltage detector threshold are also
programmable. Any of these auxiliary functions can be
disabled when not needed. All parameters are set to
default after power-on; the programmed values are
retained during sleep mode. The interface supports the
read-out of a status register, providing detailed
information about the status of the receiver and the
received data. It is also possible to store the received data
bits into the 64 bit RX FIFO register and read them out in a
buffered mode. FIFO mode can be enabled through the
SPI compatible interface by setting the fe bit to 1 in the
Output and FIFO Mode Command. During FIFO read the
crystal oscillator must be ON.