After 8
Initial
Master SPI Shift
WordA
WordB
After 8
Initial
Slave SPI Shift Register
WordB
RX Full?
Shift Register
Transmitter Buffer
Control
Master
Receiver Register
Shift Register
Transmitter Buffer
Slave
Receiver Register
SPIDAT[0]
SPIDAT[1]
MOSI
MISO
SPICLK
SPIEN (Optional)
Control
Functional Description
24.3.1.1 Two Data Pins Interface Mode
The two data pins interface mode, allows a full duplex SPI transmission where data is transmitted (shifted
out serially) and received (shifted in serially) simultaneously on separate data lines SPIDAT [0] and
SPIDAT [1]. Data leaving the master exits on transmit serial data line also known as MOSI:
MasterOutSlaveIn. Data leaving the slave exits on the receive data line also known as MISO:
MasterInSlaveOut.
McSPI has a unified SPI port control: SPIDAT [1:0] can be independently configured as receive or transmit
lines. The user has the responsibility to program which data line to use and in which direction (receive or
transmit), according to the external slave/master connection.
The serial clock (SPICLK) synchronizes shifting and sampling of the information on the two serial data
lines (SPIDAT [1:0]). Each time a bit is transferred out from the Master, one bit is transferred in from
Slave.
shows an example of a full duplex system with a Master device on the left and a Slave device
on the right. After 8 cycles of the serial clock SPICLK, the WordA has been transferred from the master to
the slave. At the same time, the 8-bit WordB has been transferred from the slave to the master.
When referring to the master device, the control block transmits the clock SPICLK and the enable signal
SPIEN (optional, see
, McSPI_MODULECTRL).
Figure 24-3. SPI Full-Duplex Transmission
24.3.1.2 Single Data Pin Interface Mode
In single data pin interface mode, under software control, a single data line is used to alternatively transmit
and receive data (Half duplex transmission).
McSPI has a unified SPI port control: SPIDAT [1:0] can be independently configured as receive or transmit
lines. The user has the responsibility to program which data line to use and in which direction (receive or
transmit), according to the external slave/master connection.
As for a full duplex transmission, the serial clock (SPICLK) synchronizes shifting and sampling of the
information on the single serial data line.
3998
Multichannel Serial Port Interface (McSPI)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated