SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
To reduce CPU load when receiving a LIN N-byte (with N = 1–8) response in interrupt mode or DMA mode, the SCI/LIN module has eight receive buffers. These buffers can store an entire LIN response in the RDy receive buffers. Figure 13-234 illustrates the receive buffers.
The checksum byte following the data bytes is validated by the internal checksum calculator. The checksum error (CE) flag indicates a checksum error and a CE interrupt is generated if enabled in the SCISETINT register.
The multibuffer 3-bit counter counts the data bytes transferred from the SCIRXSHF register to the RDy receive buffers if multibuffer mode is enabled, or to RD0 if multibuffer mode is disabled. The 3-bit compare register contains the number of data bytes expected to be received. In cases where the IDBYTE field does not convey message length (see Note: Optional Control Length Bits in Section 13.4.2.4.1.5), the LENGTH value, indicates the expected length and is used to load the 3-bit compare register. Whether the length control field or the LENGTH value is used is selectable with the COMMMODE bit.
A receive interrupt, and a receive ready RXRDY flag , and a DMA request (RXDMA) can occur after receiving a response, if there are no response receive errors for the frame (such as, there is no checksum error, frame error, and overrun error). The checksum byte is compared before acknowledging a reception. A DMA request can be generated for each received byte or for the entire response depending on whether the multibuffer mode is enabled or not (MBUFMODE bit).