14.3.3.4 Automatic FCS Check

An automatic FCS check is applied on each received frame with a frame length N ≥ 2. The RX_CRC_VALID bit in the PHY_RSSI register (PHY_RSSI.RX_CRC_VALID) is set if the FCS of a received frame is valid. The register bit is updated when issuing interrupt IRQ_3 (TRX_END) and remains valid until the next TRX_END interrupt caused by a new frame reception. In addition, bit[7] of byte RX_STATUS is set accordingly.

In Extended Operating Mode, the RX_AACK procedure does not accept a frame if the corresponding FCS is not valid, that is no IRQ_3 (TRX_END) interrupt is issued. When operating in TX_ARET mode, the FCS of a received ACK is automatically checked. If it is not correct, the ACK is not accepted.