SX1232
WIRELESS & SENSING
DATASHEET
5.5.3. Tx Processing
In Tx mode the packet handler dynamically builds the packet by performing the following operations on the payload
available in the FIFO:
Add a programmable number of preamble bytes
Add a programmable Sync word
Optionally calculating CRC over complete payload field (optional length byte + optional address byte + message) and
appending the 2 bytes checksum.
Optional DC-free encoding of the data (Manchester or whitening)
Only the payload (including optional address and length fields) is required to be provided by the user in the FIFO.
The transmission of packet data is initiated by the Packet Handler only if the chip is in Tx mode and the transmission
condition defined by TxStartCondition is fulfilled. If transmission condition is not fulfilled then the packet handler transmits a
preamble sequence until the condition is met. This happens only if the preamble length /= 0, otherwise it transmits a zero or
one until the condition is met to transmit the packet data.
The transmission condition itself is defined as:
if TxStartCondition = 1, the packet handler waits until the first byte is written into the FIFO, then it starts sending the
preamble followed by the sync word and user payload
If TxStartCondition = 0, the packet handler waits until the number of bytes written in the FIFO is equal to the number
defined in RegFifoThresh + 1
If the condition for transmission was already fulfilled i.e. the FIFO was filled in Sleep/Stdby then the transmission of
packet starts immediately on enabling Tx
5.5.4. Rx Processing
In Rx mode the packet handler extracts the user payload to the FIFO by performing the following operations:
Receiving the preamble and stripping it off
Detecting the Sync word and stripping it off
Optional DC-free decoding of data
Optionally checking the address byte
Optionally checking CRC and reflecting the result on CrcOk.
Only the payload (including optional address and length fields) is made available in the FIFO.
When the Rx mode is enabled the demodulator receives the preamble followed by the detection of sync word. If fixed
length packet format is enabled then the number of bytes received as the payload is given by the PayloadLength
parameter.
In variable length mode the first byte received after the sync word is interpreted as the length of the received packet. The
internal length counter is initialized to this received length. The PayloadLength register is set to a value which is greater
than the maximum expected length of the received packet. If the received length is greater than the maximum length stored
in PayloadLength register the packet is discarded otherwise the complete packet is received.
If the address check is enabled then the second byte received in case of variable length and first byte in case of fixed
length is the address byte. If the address matches to the one in the NodeAddress field, reception of the data continues
Rev 3 - August 2012
Page 59
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