Hi, I've been lurking in the forums for a while now, but I couldn't find a clear answer on the matter of
What do the 165 and 595 shift registers have to do with the SPI bus ?
I've seen some mentions of them being 'SPI compatibile' and instructions to connect them to SCK/MISO/MOSI pins on a AVR, but don't understand where does the SPI magic kick in.
All of the examples I've seen (except the ones I've overlooked) are (relatively) simple bit banging methods to use these ICs.
My other questions regarding this are
what benefits are there in using SPI to write to/read from these chips,
what exactly does the hardware do in these cases that would otherwise have to be done in software and
how should one properly use SPI communication with these shift registers?
The main reason behind my confusion is that I'm not very familiar with SPI and I'm getting an impression that its something more complicated then it probably is - thus I fail to see how simple ICs like 165 and 595 could actually be compatibile with such protocol.