Motorola PowerQUICC II MPC8280 Series Reference Manual page 1361

• When the SPI is a slave, SPICLK is the clock input that shifts received data in from
SPIMOSI and transmitted data out through SPIMISO. SPISEL is the enable input to
the SPI slave. In a multimaster environment, SPISEL (always an input) is used to
detect an error when more than one master is operating.
As described in Chapter 41, "Parallel I/O Ports," SPIMISO, SPIMOSI, SPICLK, and
SPISEL are multiplexed with port D[16–19] signals, respectively. They are configured as
SPI signals through the port D signal assignment register (PDPAR) and the port D data
direction register (PDDIR), specifically by setting PDPAR[DDn] and PDDIR[DRn].
39.3 Configuring the SPI Controller
The SPI can be programmed to work in a single- or multiple-master environment. This
section describes SPI master and slave operation in a single-master configuration and then
discusses the multi-master environment.
39.3.1 The SPI as a Master Device
In master mode, the SPI sends a message to the slave peripheral, which sends back a
simultaneous reply. A single master MPC8280 with multiple slaves can use
general-purpose parallel I/O signals to selectively enable slaves, as shown in Figure 39-2.
To eliminate the multimaster error in a single-master environment, the master's SPISEL
input can be forced inactive by selecting port D[19] for general-purpose I/O
(PDPAR[DD19] = 0).
MOTOROLA
Freescale Semiconductor, Inc.
Chapter 39. Serial Peripheral Interface (SPI)
For More Information On This Product,
Go to: www.freescale.com
Configuring the SPI Controller
39-3