From my understanding of how SPI interface works, the clock basically sends out data when it is set to HIGH(or LOW). So, why does it seem like in pictures of the SPI lines, the setting of HIGH and LOW appears periodically. Can't we just put data onto DATA line, turn CLOCK line on to send, then turn CLOCK line off, and repeat this process? I wrote up a program for a device implementing this, and it seems to work just fine. Also to clarify, is the CLOCK line supposed to be hooked up to a oscillator or something like that?