Serial Peripheral Interface Controller
UG0331 User Guide Revision 15.0
515
(POLL command). All other command bytes are user defined. To use the SPE, the
,
, and
bits should be set (refer to the SPI
register for bit definitions). The descriptions below assume that the frame size
(
[TXRXDFS] field) is set to 8 bits, although other frame size settings are acceptable (up to
32 bits).
14.2.2.6.1 SPI Slave Frame Format
The frame format consists of a command frame followed by 0 to 31 data frames. The size of the
command frame and data frame must be equal and is defined by TXRXDFS. A typical use model would
be to define the command frame as 8 bits followed by 31 bytes of data. This assumes
is set to
1 and TXRXDFS is set to 0x08.
The following figure shows the command and data bytes. Transmit and receive refer to the SPI
peripheral as the slave. Data bytes are optional.
Figure 218 •
SPE Command/Data Format
The first receive byte of the sequence after SPI_X_SS[x] asserts is always a command byte. The slave
always responds with a status byte, which is the contents of the
register.
Note:
Set two bits in the HWSTATUS register to facilitate additional handshaking schemes between SPI
master and SPI slave.
14.2.2.6.2 POLL Command
All command bytes except the POLL command are stored in the receive FIFO. Once received, the CMD
interrupt is generated. The command size can be set by the
register and can be 1 to 32 bits
wide, although typically commands and data will be 8 bits wide. The POLL command is encoded as 0xFF
and is the only encoded command. All other command byte encodings are user defined. If a POLL
command is received, the contents of the
register are sent back to the master and the POLL
command is discarded. It will not be stored in the FIFO.
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