NXP Semiconductors MKW01Z128, Reference Manual

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To reduce power consumption, the SPI is inactive in stop modes where the peripheral
bus clock is stopped but internal logic states are retained. If the SPI is configured as a
master, any transmission in progress stops, but is resumed after the CPU enters run
mode. If the SPI is configured as a slave, reception and transmission of a data
continues, so that the slave stays synchronized to the master.
The SPI is completely disabled in Stop modes where the peripheral bus clock is
stopped and internal logic states are not retained. When the CPU wakes from these
Stop modes, all SPI register content is reset.
Detailed descriptions of operating modes appear in Low-power mode options .
31.1.3 Block diagrams
This section includes block diagrams showing SPI system connections, the internal
organization of the SPI module, and the SPI clock dividers that control the master mode
bit rate.
31.1.3.1 SPI system block diagram
The following figure shows the SPI modules of two MCUs connected in a master-slave
arrangement. The master device initiates all SPI data transfers. During a transfer, the
master shifts data out (on the MOSI pin) to the slave while simultaneously shifting data
in (on the MISO pin) from the slave. The transfer effectively exchanges the data that was
in the SPI shift registers of the two SPI systems. The SPSCK signal is a clock output
from the master and an input to the slave. The slave device must be selected by a low
level on the slave select input (SS pin). In this system, the master device has configured
its SS pin as an optional slave select output.
Chapter 31 Serial Peripheral Interface (SPI)
MKW01Z128 MCU Reference Manual, Rev. 3, 04/2016
Freescale Semiconductor, Inc. 579