JAJSNU3 December 2023 AFE782H1 , AFE882H1
PRODUCTION DATA
The RX_IN and RX_INF pins are continuously monitored by the HART demodulator when not transmitting. AFEx82H1 requires at least 3 mark bits (3 × tBAUDHART) of 1200 Hz for carrier detection.
For UART-based communication setup, the HART data are automatically dequeued from FIFO_H2U and transmitted on the UARTOUT pin as UART characters. A delay of approximately 1.5 bit times (1.5 × tBAUDHART) occurs as a result of data decoding and synchronization from the end of the character on RX_IN or RX_INF pin until the data are enqueued into FIFO_H2U. Thus, when CD deasserts, there is typically still one UART character pending transfer to the system controller on UARTOUT (see Figure 6-24).
FIFO latency is as low as a few microseconds when using the SPI to dequeue the data from FIFO_H2U by reading FIFO_H2U_RD register. Figure 6-23 and Figure 6-24 show the timing diagrams for the start and end of the HART receive character, respectively.