I'm searching for notes/instructions about the SPI protocol from motorola.

Please help.

Hello Hannes

Welcome to the forum.
Unlike the I2C bus, there is no real protocol for the SPI bus.

Essentially, you have a clock line, a data line and an enable line. If you wish to send a byte to a peripheral, you pull is /SS line low, and then clock the data into it using the data and clock lines.
Any addressing, must be done by hardware. i.e. if you have a number of peripheral devices, you need to control the /SS lines independantly whereas with the I2C system, you send the address and then the data complete with start and stop bits.
The SPI requires more addressing logic (or more pins) than the I2C but it can transfer the data quicker. For multiple peripheral devices, the I2C bus requires less interconnection lines. I2C devices also include a higher level of digital filtering on their inputs making them more immune to noise than the SPI devices.

Does this help??

Best regards,

Yes it helps!
Thank you