12.3.6 SPI Clocking Schemes
The clock polarity select bit (CLKPOLARITY) and the clock phase select bit (CLK_PHASE) control four different
clocking schemes on the SPICLK pin. CLKPOLARITY selects the active edge, either rising or falling, of the
clock. CLK_PHASE selects a half-cycle delay of the clock. The four different clocking schemes are as follows:
• Falling Edge Without Delay. The SPI transmits data on the falling edge of the SPICLK and receives data on
the rising edge of the SPICLK.
• Falling Edge With Delay. The SPI transmits data one half-cycle ahead of the falling edge of the SPICLK
signal and receives data on the falling edge of the SPICLK signal.
• Rising Edge Without Delay. The SPI transmits data on the rising edge of the SPICLK signal and receives
data on the falling edge of the SPICLK signal.
• Rising Edge With Delay. The SPI transmits data one half-cycle ahead of the rising edge of the SPICLK signal
and receives data on the rising edge of the SPICLK signal.
The selection procedure for the SPI clocking scheme is shown in
. Examples of these four clocking
schemes relative to transmitted and received data are shown in
.
Table 12-3. SPI Clocking Scheme Selection Guide
SPICLK Scheme
CLKPOLARITY
Rising edge without delay
0
0
Rising edge with delay
0
1
Falling edge without delay
1
0
Falling edge with delay
1
1
(1)
The description of CLK_PHASE and CLKPOLARITY differs between manufacturers. For proper
operation, select the desired waveform to determine the clock phase and clock polarity settings.
SPICLK cycle
number
1
2
3
4
5
6
7
8
SPICLK
(Falling edge
without delay)
SPICLK
(Falling edge
with delay)
SPISIMO/
SPISOMI
SPISTE
MSB
LSB
Note:
Previous data bit
(Into slave)
Receive latch
points
SPICLK
(Rising edge
without delay)
SPICLK
(Rising edge
with delay
)
See note
Figure 12-6. SPICLK Signal Options
Serial Peripheral Interface (SPI)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
771
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
Страница 2: ......