Rev1.0a | 39/50
CMT2300A
6. Packet Handler
CMT2300A supports direct mode and packet mode:
Direct Mode
– In Rx mode, only supports preamble and sync detection, FIFO does not work, demodulated data sent out
from GPIO. In Tx mode, only supports transmitting the data input from GPIO.
Packet Mode
– Supports all packet formats, demodulated data is stored in FIFO, accessed by SPI.
6.1 Direct Mode
MODEM
data
clock
1
1
User Registers
EEPROM (CMT Parameters)
RF
SPI
CSB
SCLK
SDIO
DCLK
DOUT/DIN
Preamble (Opt)
Sync (Opt)
data
clock
1
1
INT1/INT2
Figure 5. Direct mode data path
Rx processing
In direct mode, the data from the demodulator is sent directly to the external MCU via the DOUT pin. DOUT can be set to GPIO1,
2 or 3. The typicalRX direct mode control sequence for the MCU is:
1. Configures GPIOsusing theCUS_IO_SEL register.
2. Configures DATA_MODE = 0.
3. Send the go_rx command.
4. Capture the data from DOUT continuously.
5. Send the go_sleep/go_stby/go_rfs command to stop receiving and save the power.
Tx processing
In the direct mode, the data to be transmitted is sent directly to the chip from the external MCU by via DIN pin. The data rate is
determined by the MCU but must be less than +/- 30% of the data rate configured on the RFPDK. The typical TX direct mode
control sequence for the MCU is:
1. Set register TX_DIN_EN to 1 to enable DIN on GPIO.
2. Set TX_DIN_SEL to 0 to configure GPIO1 as DIN, or 1 to configure GPIO2 as DIN.
3. Send the go_tx command,send in the data to the DIN pinwith the desired data rate, the data is transmitted immediately.
4. Send the go_sleep/go_stby/go_rfs command to stop transmission and save the power.