How's this for an SPI timing diagram?
SPI is a completely meaningless initialism.
The timing diagram you posted is not what we think of as "SPI" -- it's just a wacky synchronous serial interface.
The hilarious -- by which I mean "completely hateful" -- thing is that nonstandard wacky synchronous serial interfaces are, uh, standard on low-pin-count multichannel converter chips.
The interfaces are all pretty goddamn stupid.
And this is one reason why I'm thankful I use FPGAs to talk to them. Instead of trying to force a microcontroller's standard SPI or USART peripheral to deal with these things, I just code up the exact interface I need. This of course assumes that the data sheet is comprehensive and correct.
In the "jeez, it would be nice" category: It Would Be Nice if the converter manufacturers could supply a bus-function HDL model of their parts for the customers to use to verify their FPGA designs, so I don't have to write them. There is nothing like using the same assumptions for design in the verification, right?
And It Would Be Really Fucking Nice if the manufacturer tech support response to "Do you have VHDL models of your converter ADCxxxx?" was
not "You can find the IBIS models here ..."
Anyway.