I don't use the chip select feature in the SPI module since SD transfers are so large.
To use this feature you must select the proper pin multiplexing mode with the Port Control Module.
See chapter 10 and 11 of the chip data sheet.
Chapter 10
Signal Multiplexing and Signal Descriptions
10.1 Introduction
To optimize functionality in small packages, pins have several functions available via
signal multiplexing. This chapter illustrates which of this device's signals are multiplexed
on which external pin.
The Port Control block controls which signal is present on the external pin. Reference
that chapter to find which register controls the operation of a specific pin.
Chapter 11
Port control and interrupts (PORT)
11.1 Introduction
NOTE
For the chip-specific implementation details of this module's
instances see the chip configuration chapter.
11.1.1 Overview
The port control and interrupt (PORT) module provides support for port control, and
external interrupt functions. Most functions can be configured independently for each pin
in the 32-bit port and affect the pin regardless of its pin muxing state.
There is one instance of the PORT module for each port. Not all pins within each port are
implemented on a specific device.
I am not very knowledgeable about the Kinetis chip, Paul Stoffregen helped me configure the SPI to be compatible with his software for Teensy 3.0.