When is radio CRCSTATUS register updated?

[abkirchhoff]

I am using the nRF52840 with the SoftDevice disabled to run a proprietary RF protocol. For much of the time, I have the radio in continuous receive mode by making use of the END-START shortcut. I update the PACKETPTR each time I receive the ADDRESS event so as not to overwrite packets. For each packet received, I would like to record the CRC status.

After the first packet is received (END event), the CRCSTATUS register is updated. Does the CRCSTATUS register remain valid for the first packet even after receiving the ADDRESS event for the second packet?

Asked another way, is the CRCSTATUS register only changed when an END event occurs or is the register changed at other times?

Thanks!

[bjorn-spockeli]

Hi Austin, 

After the first packet is received (END event), the CRCSTATUS register is updated. Does the CRCSTATUS register remain valid for the first packet even after receiving the ADDRESS event for the second packet?

 According to the CRC setion in the nRF52840 Product Specification, the CRC generator in the RADIO calculates the CRC over the whole packet excluding the preamble. Hence, the CRC generator will start running as the first address bit is feed serially into the generator. As the CRCSTATUS is the result of the comparison of the output of the CRC generator against the CRC in the on-air packet, the CRCSTATUS register will only be updated after the entire packet has been received,i.e. when the END event is generated. 

 

Asked another way, is the CRCSTATUS register only changed when an END event occurs or is the register changed at other times?

 Yes, CRCSTATUS is only updated after the END event occurs. 

Best regards

Bjørn

[abkirchhoff]

Bjorn,

Thanks for your reply. This was my interpretation of the product spec as well, but I wanted to verify that the CRCSTATUS register was not reset when the CRC generator starts with the first address bit.

Austin