SPICLK Edge Nr.
Sample
End
Begin
SPICLK (POL=0)
SPICLK (POL=1)
Data From the Master
Data From the Slave
Slave Select
(SPIEN) (optional)
1 2
3
4
5
6
7
8
9
10
11 12
13
14
15
16
MSB
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
LSB
MSB
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
LSB
t
LEAD
t
LAG
Transfer
Preliminary
www.ti.com
Architecture
12.2.2.3.8 Transfer Format With PHA = 1
This section describes SPI full duplex transmission with the SPI mode1 and the SPI mode3.
In the transfer format with PHA = 1, SPIEN is activated a delay (t
Lead
) ahead of the first SPICLK edge.
In both master and slave modes, McSPI drives the data lines on the first SPICLK edge.
Each data frame is transmitted starting with the MSB. At the extremity of both SPI data lines , the first
bit of SPI word is valid on the next SPICLK edge, a half cycle of SPICLK later. It is the sampling edge
for both the master and slave.
When the third edge occurs, the received data bit is shifted into the shift register. The next data bit of
the master is provided to the serial input pin of the slave.
This process continues for a total of pulses on the SPICLK line defined by the word length programmed
in the master device, with data being latched on even numbered edges and shifted on odd numbered
edges.
is a timing diagram of a SPI transfer for the SPI mode1 and the SPI mode3, when McSPI is
master or slave, with the frequency of SPICLK equals to the frequency of CLKSPIREF. It should not be
used as a replacement for SPI timing information and requirements detailed in [3].
The SPIEN line may remain active between successive transfers. In 3-pin mode without using the
SPIEN signal, the controller provides the same waveform but with SPIEN forced to low state. In slave
mode SPIEN is useless.
Figure 12-7. Full Duplex Single Transfer Format With PHA = 1
1221
SPRUGX9 – 15 April 2011
Multichannel Serial Port Interface (McSPI)
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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