I want to make a tutorial on how shift registers and SPI work, but I am having trouble understanding it myself. I know how to chain shift registers using the last output pin, but in this logic diagram, why is the cascade output on the right called QH' and not just QH? Don't the two inverters make it QH again? Here is another logic diagram made by another company, same chip, but it is even more confusing.
Both of those shift registers have latched outputs. QH' is not latched. The other non-latched outputs are not available external to the chip.
With a regular (non-latched) shift register, the shifting data appears at the outputs as it's shifted and you wouldn't need a separate cascade output.
I want to make a tutorial on how shift registers and SPI work, but I am having trouble understanding it myself.
Maybe start with D-type flip-flops. Then with two or more flip-flops cascaded together to make a shift register. Then, with additional flip-flops for latching.
Don't get too hung-up on pin names. Each pin is going to have it's own name, so a buffered output will have a different name than a non-buffered output. You could change the name of QH to Q7 (with the "bits" numbered 0-7). Different manufactures may use different names for the same pin. Or if you have two cascaded 8-bit registers, the outputs of your complete 16-bit circuit could be named Q0 through Q15, etc.
The manufacturer's data sheet will give a list of pin numbers, names, and functions, and sometimes a simplified schematic. Sometimes you need ALL of that information.
Ah I see, so the prime mark simply indicates that it is not the same point as the regular QH. I thought it meant the inverse. That makes things more clear.