6.10.3 Reception of Air Interface Data

At the start of a receive operation (when SOF is successfully detected), B6 is set in the IRQ Status register. An RX complete interrupt request is sent to the MCU at the end of the receive operation if the receive data string is shorter than or equal to the number of bytes configured in the Adjustable FIFO IRQ Levels register (0x14). An IRQ_FIFO interrupt request is sent to the MCU during the receive operation if the data string is greater than the level set in the Adjustable FIFO IRQ Levels register (0x14). After receiving an IRQ_FIFO or RX complete interrupt, the MCU must read the FIFO Status register (0x1C) to determine the number of bytes to be read from the FIFO. Next, the MCU must read the data in the FIFO. It is optional but recommended to read the FIFO Status register (0x1C) after reading FIFO data to determine if the receive is complete. In the case of an IRQ_FIFO, the MCU should expect either another IRQ_FIFO or RX complete interrupt. This is repeated until an RX complete interrupt is generated. The MCU receives the interrupt request, then checks to determine the reason for the interrupt by reading the IRQ Status register (0x0C), after which the MCU reads the data from the FIFO.

If the reader detects a receive error, the corresponding error flag is set (framing error, CRC error) in the IRQ Status register, indicating to the MCU that reception was not completed correctly.