PXD10RM Datasheet, PDF (307/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

The DSPIx_CTAR0–DSPIx_CTAR7 registers hold clock and transfer attributes.The SPI configuration can
select which CTAR to use on a frame by frame basis by setting the CTAS field in the DSPIx_PUSHR.
The 16-bit shift register in the master and the 16-bit shift register in the slave are linked by the SOUT_x
and SIN_x signals to form a distributed 32-bit register. When a data transfer operation is performed, data
is serially shifted a predetermined number of bit positions. Because the registers are linked, data is
exchanged between the master and the slave; the data that was in the master’s shift register is now in the
shift register of the slave, and vice versa. At the end of a transfer, the TCF bit in the DSPIx_SR is set to
indicate a completed transfer. Figure 11-11 illustrates how master and slave data is exchanged.
DSPI Master
Shift register
Baud rate generator
SIN_x SOUT_x
SOUT_x SIN_x
SCK_x SCK_x
CS_x CS0_x
DSPI Slave
Shift register
Figure 11-11. SPI Serial Protocol Overview
The DSPI has three peripheral chip select (CSx) signals that are be used to select which of the slaves to
communicate with.
Transfer protocols and timing properties are shared by the three DSPI configurations; these properties are
described independently of the configuration in Section 11.8.5, Transfer Formats. The transfer rate and
delay settings are described in section Section 11.8.4, DSPI Baud Rate and Clock Delay Generation.
Refer to Section 11.8.8, Power Saving Features for information on the power-saving features of the DSPI.
11.8.1 Modes of Operation
The DSPI modules have five available distinct modes:
• Master mode
• Slave mode
• Module disable mode
• External stop mode
• Debug mode
Master, slave, and module disable modes are module-specific modes. The external stop and debug modes
are device-specific modes.
The module-specific modes are determined by bits in the DSPIx_MCR. The device-specific modes are
modes that the entire device can enter in parallel with the DSPI being configured in one of its
module-specific modes.
Freescale Semiconductor
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
11-25