RFM66W Datasheet, PDF (60/87 Pages) List of Unclassifed Manufacturers – 868 & 915MHz Ultra Low Power High Link Budget Integrated UHF Transceiver

WIRELESS & SENSING
RFM66W
DATASHEET
Address filtering can be enabled via the AddressFiltering bits. It adds another level of filtering, above Sync word (i.e. Sync
must match first), typically useful in a multi-node networks where a network ID is shared between all nodes (Sync word)
and each node has its own ID (address).
Two address based filtering options are available:
 AddressFiltering = 01: Received address field is compared with internal register NodeAddress. If they match then
the packet is accepted and processed, otherwise it is discarded.
 AddressFiltering = 10: Received address field is compared with internal registers NodeAddress and
BroadcastAddress.
If either is a match, the received packet is accepted and processed, otherwise it is discarded. This additional check with
a constant is useful for implementing broadcast in a multi-node networks
Please note that the received address byte, as part of the payload, is not stripped off the packet and is made available in
the FIFO. In addition, NodeAddress and AddressFiltering only apply to Rx. On Tx side, if address filtering is expected, the
address byte should simply be put into the FIFO like any other byte of the payload.
As address filtering requires a Sync word match, both features share the same interrupt flag SyncAddressMatch.
5.5.6.3. Length Based
In variable length Packet mode, PayloadLength must be programmed with the maximum payload length permitted. If
received length byte is smaller than this maximum then the packet is accepted and processed, otherwise it is discarded.
Please note that the received length byte, as part of the payload, is not stripped off the packet and is made available in the
FIFO.
To disable this function the user should set the value of the PayloadLength to 2047.
5.5.6.4. CRC Based
The CRC check is enabled by setting bit CrcOn in RegPacketConfig1. It is used for checking the integrity of the message.
 On Tx side a two byte CRC checksum is calculated on the payload part of the packet and appended to the end of
the message
 On Rx side the checksum is calculated on the received payload and compared with the two checksum bytes received.
The result of the comparison is stored in bit CrcOk.
By default, if the CRC check fails then the FIFO is automatically cleared and no interrupt is generated. This filtering function
can be disabled via CrcAutoClearOff bit and in this case, even if CRC fails, the FIFO is not cleared and only PayloadReady
interrupt goes high. Please note that in both cases, the two CRC checksum bytes are stripped off by the packet handler
and only the payload is made available in the FIFO.
Two CRC implementations are selected with bit CrcWhiteningType.
Table 28 CRC Description
Crc Type
CCITT
IBM
CrcWhiteningType
0 (default)
1
Polynomial
X¹⁶ + X¹² + X⁵ + 1
X¹⁶ + X¹⁵ + X² + 1
Seed Value
0x1D0F
0xFFFF
A C code implementation of each CRC type is proposed in Application Section 7.
Complemented
Yes
No
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