Figure 3.2.3
Figure 3.2.4
The host should use the following steps to fetch data from a DNT90M SPI slave, as show in Figure 3.2.5:
1. The host sets the /HOST_RTS signal high to allow the DNT90M to signal data available.
2. The DNT90M sets the data available (DAV) high to signal the host it has data.
3. The host set the /SS signal low to enable SPI operation.
4. The host clocks in one dummy byte (ignore the output byte) and then sets /HOST_RTS low.
5. The host begins to clock out the data, which can include several messages.
6. The host continues to clock out data until a 0x00 byte occurs in the byte stream where a 0xFB start-of-message
would be expected.
7. The host has now clocked out all messages and the 0x00 is discarded.
8. The host sets /HOST_RTS and /SS high to allow the DNT90M to signal DAV the next time it
has data.
Note that the DAV signal can go low before the last message is clocked out. It is not a reliable indication that the last byte
of the message(s) has been clocked out. See Section 5.2 for recommendations on configuring the SPI port, and Section
7.4.4 for detailed information on SPI port configuration parameters.
©2012 by Murata Electronics N.A., Inc.
DNT90M Integration Guide (2012/09/17)
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