33.6.4.1.2 Host DMA

When using the I²C host with DMA, the ADDR register must be written with the desired address (ADDR.ADDR), transaction length (ADDR.LEN), and transaction length enable (ADDR.LENEN). When ADDR.LENEN is written to 1 along with ADDR.ADDR, ADDR.LEN determines the number of data bytes in the transaction from 0 to 255. DMA is then used to transfer ADDR.LEN bytes followed by an automatically generated NACK (for host reads) and a STOP.

If a NACK is received by the client for a host write transaction before ADDR.LEN bytes, a STOP will be automatically generated and the length error (STATUS.LENERR) will be raised along with the INTFLAG.ERROR interrupt.

The I²C host generates the following requests:

• Read data received (RX): The request is set when host read data is received. The request is cleared when DATA is read.
• Write data needed for transmit (TX): The request is set when data is needed for a host write operation. The request is cleared when DATA is written.