SLLSFR8 Data sheet

7.6.3.1 SPI Transmit FIFO (address = h1010)

The transmit FIFO is write only and is written to when a write command is issued to its address. Transmission will begin when the entire frame has been written into the buffer. All data bytes written after the end of the frame is ignored until a new transmit FIFO write is started. All writes to a transmit FIFO should be directed at the main address only, as each byte that is written is automatically shifted into the FIFO. For example, writing larger SPI messages than can be transferred in a single CAN message occurs over multiple CAN writes to the same address, since the SPI header bytes will tell the device how many data bytes to expect.

The size of each frame in the TX buffer is determined by the message length. There is a 2-byte header required at the beginning of each SPI FIFO element. The total length of the TX frame in the buffer is the sum of

2 bytes for the SPI header
Message length of data bytes

See SPI Control Protocol for more information and examples.

Note: If the transmit FIFO is full, any new messages written to it are discarded and an interrupt is set.

TCAN5102-Q1 SPI TX FIFO Write Header
(Header and Data Only)

Figure 7-76 SPI TX FIFO Write Header (Header and Data Only)

TCAN5102-Q1 Example SPI TX FIFO Header
(Standard CAN Frame Format)

Figure 7-77 Example SPI TX FIFO Header (Standard CAN Frame Format)

Figure 7-78 SPI Transmit FIFO

Table 7-119 SPI Transmit FIFO Descriptions

Byte	Bit	Field	Type	Reset	Description
0	7	STORE_RX	W	0	Whether to store the POCI data for this message in the receive FIFO 0 = Do not store any data in the receive FIFO 1 = Save the received POCI data in the receive FIFO for this message
	6:3	RSVD	R	0	Reserved
	2:0	CHAN	W	0x0	SPI Channel that was used for this message Valid values 0-3 0 = SPI channel 0 1 = SPI channel 1 2 = SPI channel 2 3 = SPI channel 3 4 = SPI channel 4 5 = SPI channel 5 6 = SPI channel 6 7 = SPI channel 7 Note: A SPI channel corresponds to a specific GPIO and requires that GPIO to be assigned as a special function
1	7:0	NUM_BYTES	W	0x0	Number of bytes in the SPI frame (does NOT include the above header bytes) Valid values 1-255. 0 is invalid.