FPGA Registers
EPU-4562 Programmer’s Reference Manual
20
SPI
D
ATA
R
EGISTERS
There are four data registers used on the SPI interface. How many are used depends on the
device being communicated with. SPIDATA0 is typically the least significant byte and
SPIDATA3 is the most significant byte. Any write to the most significant byte SPIDATA3
initiates the SCLK and, depending on the MAN_SS state, will assert a slave select to begin an
SPI bus transaction.
Data is sent according to the LSBIT_1ST setting. When LSBIT_1ST = 0, the MSbit of
SPIDATA3 is sent first and received data will be shifted in the LSbit of the selected frame size
determined by SPILEN1 and SPILEN0. When LSBIT_1ST = 1, the LSbit of the selected frame
size is sent first and the received data will be shifted in the MSbit of SPIDATA3.
SPIDATA0 (Least Significant Byte)
D7
D6
D5
D4
D3
D2
D1
D0
MSB
LSB
SPIDATA1
D7
D6
D5
D4
D3
D2
D1
D0
MSB
LSB
SPIDATA2
D7
D6
D5
D4
D3
D2
D1
D0
MSB
LSB
SPIDATA3 (Most Significant Byte) [Cycle Trigger Register]
D7
D6
D5
D4
D3
D2
D1
D0
MSB
LSB