RF64 datasheet(52/76 Pages) ETC2

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ADVANCED COMMUNICATIONS & SENSING

Page 52 of 76

RF64

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By default, if the CRC check is enabled and fails for the current packet, then the FIFO is automatically cleared and

neither of the two interrupts are generated and new packet reception is started. This autoclear function can be

disabled via PKTParam_CRC_autoclr bit and, in this case, even if CRC fails, the FIFO is not cleared and only

Payload_ready IRQ source is asserted.

Once

fully

received,

the

payload

can

also

fully

partially

retrieved

Stby

mode

via

PKTParam_Fifo_stby_access. At the end of the reception, although the FIFO automatically stops being filled, it is

still up to the user to explicitly exit Rx mode if required. (e.g. go to Stby to get payload). FIFO must be empty for a

new packet reception to start.

5.5.5. Packet Filtering

RF64

‟s packet handler offers several mechanisms for packet filtering ensuring that only useful packets are made

available to the uC, reducing significantly system power consumption and software complexity.

5.5.5.1. Sync Word Based

Sync word filtering/recognition is automatically enabled in Packet mode. It is used for identifying the start of the

payload and also for network identification. As previously described, the Sync word recognition block is configured

(size, error tolerance, value) via RXParam_Sync_size, RXParam_Sync_tol and SYNCParam configuration

registers. This information is used, both for appending Sync word in Tx, and filtering packets in Rx.

Every received packet which does not start with this locally configured Sync word is automatically discarded and no

interrupt is generated.

When the Sync word is detected, payload reception automatically starts and Sync IRQ source is asserted.

5.5.5.2. Address Based

Address filtering can be enabled via the PKTParam_Adrs_filt bits. It adds another level of filtering, above Sync

word, 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).

Three address based filtering options are available:

 Adrs_filt = 01: Received address field is compared with internal register Node_Adrs. If they match then the

packet is accepted and processed, otherwise it is discarded.

 Adrs_filt = 10: Received address field is compared with internal register Node_Adrs and the constant 0x00. 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.

 Adrs_filt = 11: Received address field is compared with internal register Node_Adrs and the constants 0x00 &

0xFF. If any of the three matches, then the received packet is accepted and processed, otherwise it is

discarded. These additional checks with constants are useful for implementing broadcast commands of all

nodes.

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, Node_Adrs and Adrs_filt 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.

5.5.5.3. Length Based

In variable length Packet mode, PKTParam_Payload_length must be programmed with the maximum length

permitted. If received length byte is smaller than this maximum then the packet is accepted and processed,

otherwise it is discarded.

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