NRF52820-QDAA-R datasheet(165/437 Pages) NORDIC

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Peripherals

6.12.3 Data whitening

The RADIO is able to do packet whitening and de-whitening, enabled in PCNF1.WHITEEN. When enabled,

whitening and de-whitening will be handled by the RADIO automatically as packets are sent and received.

The whitening word is generated using polynomial g(D) = D7+ D4 + 1, which then is XORed with the

data packet that is to be whitened, or de-whitened. The linear feedback shift register is initialized via

DATAWHITEIV. See the following figure.

Data in

Data out

Position

Figure 50: Data whitening and de-whitening

Whitening and de-whitening will be performed over the whole packet except for the preamble and the

address fields.

6.12.4 CRC

The CRC generator in RADIO calculates the CRC over the whole packet excluding the preamble. If desirable,

the address field can be excluded from the CRC calculation as well.

See CRCCNF register for more information.

The CRC polynomial is configurable as illustrated in the following figure, where bit 0 in the CRCPOLY

information.

Packet

(Clocked in serially)

Xn-1

Figure 51: CRC generation of an n bit CRC

The figure shows that the CRC is calculated by feeding the packet serially through the CRC generator.

Before the packet is clocked through the CRC generator, the CRC generator's latches b0 through bn will

be initialized with a predefined value specified in the CRCINIT register. After the whole packet has been

clocked through the CRC generator, b0 through bn will hold the resulting CRC. This value will be used by the

RADIO during both transmission and reception. Latches b0 through bn are not available to be read by the

CPU at any time. However, a received CRC can be read by the CPU via the RXCRC register.

The length (n) of the CRC is configurable, see CRCCNF for more information.

Once the entire packet, including the CRC, has been received and no errors were detected, RADIO

generates a CRCOK event. If CRC errors were detected, a CRCERROR event is generated.

The status of the CRC check can be read from the CRCSTATUS register after a packet has been received.

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NRF52820-QDAA-R Datasheet(PDF) 165 Page - Nordic Semiconductor