12.3.4 Data Format
The four-bit SPICHAR register field specifies the number of bits in the data character (1 to 16). This information
directs the state control logic to count the number of bits received or transmitted to determine when a complete
character has been processed.
The following statements apply to characters with fewer than 16 bits:
• Data must be left-justified when written to SPIDAT and SPITXBUF.
• Data read back from SPIRXBUF is right-justified.
• SPIRXBUF contains the most recently received character, right-justified, plus any bits that remain from
previous transmission(s) that have been shifted to the left (shown in
Example 12-1. Transmission of Bit from SPIRXBUF
Conditions:
1. Transmission character length = 1 bit (specified in SPICHAR bits)
2. The current value of SPIDAT = 737Bh
SPIDAT (before transmission)
0
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
SPIDAT (after transmission)
(TXed) 0 ←
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
← (RXed)
SPIRXBUF (after transmission)
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
(1)
x = 1, if SPISOMI data is high; x = 0, if SPISOMI data is low; master mode is assumed.
Serial Peripheral Interface (SPI)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
769
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
Страница 2: ......