SPI 1 Programming Model
Serial Peripheral Interface 1 and 2 13-5
13.3.2 SPI 1 Transmit Data Register
This write-only data register is the top of the 8×16 TxFIFO. Writing to TxFIFO is permitted as long as
TxFIFO is not full, even if the XCH bit is set. For example, a user may write to TxFIFO during the SPI
data exchange process. In either master or slave mode, a maximum of 8 data words are loaded. Data
written to this register can be of either 8-bit or 16-bit size. The number of bits to be shifted out of a 16-bit
FIFO element is determined by the bit count setting in the SPI 1 status/control register. The unused MSBs
are discarded and may be written with any value. For example, to transfer 10-bit data, a 16-bit word is
written to the SPITXD register, and the 6 MSBs are treated as “don’t care” and will not be shifted out. In
slave mode, if no data is loaded to the TxFIFO, ze ro s are shifted out serially as the TxD signal. Writes to
this register are ignored while the SPIEN bit in the SPI 1 control/status register is clear. The bit position
assignments for this register are shown in the following register display. The settings for this register are
described in Table13-2.

SPITXD SPI 1 Transmit Data Register 0x(FF)FFF7 02

BIT 7 654321BIT 0
DATA
TYPE wwwwwwww
RESET 00000000
0x00
Table 13-2. SPI 1 Transmit Data Register Description
Name Description Setting
DATA
Bits 7–0 Data—Top SPI data to be loaded to the 8× 16 TxFIFO See description