Datasheet
Serial Peripheral Interface (S08SPI16V1)
MC9S08JM60 Series Data Sheet, Rev. 3
Freescale Semiconductor 267
15.5 Initialization/Application Information
15.5.1 SPI Module Initialization Example
15.5.1.1 Initialization Sequence
Before the SPI module can be used for communication, an initialization procedure must be carried out, as
follows:
1. Update control register 1 (SPIxC1) to enable the SPI and to control interrupt enables. This register
also sets the SPI as master or slave, determines clock phase and polarity, and configures the main
SPI options.
2. Update control register 2 (SPIxC2) to enable additional SPI functions such as the SPI match
interrupt feature, the master mode-fault function, and bidirectional mode output. 8- or 16-bit mode
select and other optional features are controlled here as well.
3. Update the baud rate register (SPIxBR) to set the prescaler and bit rate divisor for an SPI master.
4. Update the hardware match register (SPIxMH:SPIxML) with the value to be compared to the
receive data register for triggering an interrupt if hardware match interrupts are enabled.
5. In the master, read SPIxS while SPTEF = 1, and then write to the transmit data register
(SPIxDH:SPIxDL) to begin transfer.
15.5.1.2 Pseudo—Code Example
In this example, the SPI module will be set up for master mode with only hardware match interrupts
enabled. The SPI will run in 16-bit mode at a maximum baud rate of bus clock divided by 2. Clock phase
and polarity will be set for an active-high SPI clock where the first edge on SPSCK occurs at the start of
the first cycle of a data transfer.
SPIxC1=0x54(%01010100)
Bit 7 SPIE = 0 Disables receive and mode fault interrupts
Bit 6 SPE = 1 Enables the SPI system
Bit 5 SPTIE = 0 Disables SPI transmit interrupts
Bit 4 MSTR = 1 Sets the SPI module as a master SPI device
Bit 3 CPOL = 0 Configures SPI clock as active-high
Bit 2 CPHA = 1 First edge on SPSCK at start of first data transfer cycle
Bit 1 SSOE = 0 Determines SS
pin function when mode fault enabled
Bit 0 LSBFE = 0 SPI serial data transfers start with most significant bit