SPRUIM2H May 2020 – October 2023 AM2431 , AM2432 , AM2434 , AM6411 , AM6412 , AM6421 , AM6422 , AM6441 , AM6442
The FSI module transmits and receives information in frames. Each frame contains multiple phases where different information can be found. The number of phases as well as the total length of the frame varies depending on the frame type being transmitted. Frames can be as short as 16-bits long for a ping or error frame or 288-bits long for a 16-word data frame.
In normal transmission mode, there are four preamble clock edges before the start of the frame and four post-frame clock edges (postamble). Data is transmitted on both edges of the clock (double data rate). The basic frame structure is shown in Table 12-4462. Each phase of the frame (such as start-of-frame, frame type, and so on) is transmitted with the most-significant bit first. Table 12-4462 describes the basic frame structure used by the FSI and adapted according to which frame type is transmitted.
Idle State | Preamble | Start of Frame | Frame Type | User Data | Data Words | CRC Byte | Frame Tag | End of Frame | Postamble | Idle State |
---|---|---|---|---|---|---|---|---|---|---|
1111 | 1001 | 4 bits | 8 bits | 1-16 words |
8 bits | 4 bits | 0110 | 1111 |
The FSI also supports a FSI-SPI compatibility mode. The SPI compatible frame structure is similar to a standard FSI frame, but there are differences. Refer to Section 12.4.5.4.9 for more information on how to configure and use the FSI-SPI compatibility mode.
The terms “frame” and “packet” can be used interchangeably to describe the signaling format of the FSI.