To decrypt a packet received by the radio immediately upon its reception, CCM can be started when the RADIO PAYLOAD event is generated. The packet is decrypted when the CCM.END event is generated. Typically, CCM will decrypt the packet before or during the reception of the CRC. However, if the packet is large and the bitrate is high, CCM will not finish before the PHYEND event, but shortly afterward. After the CCM.END event is generated; the MACSTATUS can be checked.
AES CCM must therefore operate on the same memory location as RADIO, as illustrated in the following figure.